diff --git a/02-top-level-menu-features.html b/02-top-level-menu-features.html
index 0c6e64d..8fd4a27 100644
--- a/02-top-level-menu-features.html
+++ b/02-top-level-menu-features.html
@@ -471,7 +471,7 @@ <h3 class="callout-title">Name three other tools or features that can be changed
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Click on the gear icon in the main window or go to Tools →
 Preferences</li>
diff --git a/07-manipulating-MARC-data-advanced.html b/07-manipulating-MARC-data-advanced.html
index 2064a8e..9c6f3d0 100644
--- a/07-manipulating-MARC-data-advanced.html
+++ b/07-manipulating-MARC-data-advanced.html
@@ -488,7 +488,7 @@ <h3 class="callout-title">Use the Build New Field to add a proxy to the
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools → Build New Field</li>
 <li>In the new window, in the field box, type in
@@ -577,7 +577,7 @@ <h3 class="callout-title">Run the RDA Helper on your MARC data</h3>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select RDA Helper</li>
diff --git a/08-tasks-and-automation.html b/08-tasks-and-automation.html
index 06c7211..0cf8368 100644
--- a/08-tasks-and-automation.html
+++ b/08-tasks-and-automation.html
@@ -520,7 +520,7 @@ <h3 class="callout-title">Create and run a new Task that runs the RDA helper and
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select Manage Tasks</li>
@@ -573,7 +573,7 @@ <h3 class="callout-title">Add a proxy to the <code>856 40$u</code> in
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select Manage Tasks</li>
diff --git a/aio.html b/aio.html
index 91be988..842d2eb 100644
--- a/aio.html
+++ b/aio.html
@@ -690,7 +690,7 @@ <h3 class="callout-title">Name three other tools or features that can be changed
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Click on the gear icon in the main window or go to Tools →
@@ -2232,7 +2232,7 @@ <h3 class="callout-title">Use the Build New Field to add a proxy to the
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools → Build New Field</li>
@@ -2333,7 +2333,7 @@ <h3 class="callout-title">Run the RDA Helper on your MARC data</h3>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
@@ -2593,7 +2593,7 @@ <h3 class="callout-title">Create and run a new Task that runs the RDA helper and
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
@@ -2652,7 +2652,7 @@ <h3 class="callout-title">Add a proxy to the <code>856 40$u</code> in
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
diff --git a/index.html b/index.html
index 15e1b31..f616c6d 100644
--- a/index.html
+++ b/index.html
@@ -372,7 +372,8 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 <div id="prerequisites" class="callout-inner">
 <h3 class="callout-title">Prerequisites</h3>
 <div class="callout-content">
-<p>This lesson requires a basic knowledge of the MARC21 standard.</p>
+<p>This lesson requires a <a href="https://www.loc.gov/marc/96principl.html" class="external-link">basic knowledge</a> of
+the <a href="https://www.loc.gov/marc/" class="external-link">MARC21 standard</a>.</p>
 </div>
 </div>
 </div>
diff --git a/instructor/02-top-level-menu-features.html b/instructor/02-top-level-menu-features.html
index 5f385e1..7492a63 100644
--- a/instructor/02-top-level-menu-features.html
+++ b/instructor/02-top-level-menu-features.html
@@ -407,7 +407,7 @@ <h3 class="card-title">Objectives</h3>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: A number of differences have been noted in the Top Level Menu
 design and features for Mac users in this lesson: - Help is in the top
@@ -490,7 +490,7 @@ <h3 class="callout-title">Name three other tools or features that can be changed
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Click on the gear icon in the main window or go to Tools →
 Preferences</li>
diff --git a/instructor/03-working-with-MARC-files.html b/instructor/03-working-with-MARC-files.html
index f0ba563..bc33015 100644
--- a/instructor/03-working-with-MARC-files.html
+++ b/instructor/03-working-with-MARC-files.html
@@ -683,7 +683,7 @@ <h3 class="callout-title">Behavior when you reset your preferences and other pop
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: Some preference updates will force MarcEdit to restart and
 others will not. Also note that in order for some preference changes to
diff --git a/instructor/07-manipulating-MARC-data-advanced.html b/instructor/07-manipulating-MARC-data-advanced.html
index 6f4d599..71b49f4 100644
--- a/instructor/07-manipulating-MARC-data-advanced.html
+++ b/instructor/07-manipulating-MARC-data-advanced.html
@@ -490,7 +490,7 @@ <h3 class="callout-title">Use the Build New Field to add a proxy to the
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools → Build New Field</li>
 <li>In the new window, in the field box, type in
@@ -579,7 +579,7 @@ <h3 class="callout-title">Run the RDA Helper on your MARC data</h3>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select RDA Helper</li>
diff --git a/instructor/08-tasks-and-automation.html b/instructor/08-tasks-and-automation.html
index 9fab86d..49ebb2a 100644
--- a/instructor/08-tasks-and-automation.html
+++ b/instructor/08-tasks-and-automation.html
@@ -477,7 +477,7 @@ <h3 class="card-title">Objectives</h3>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: “Task Actions” and “Manage Existing Tasks” menu options are
 different on a Mac.</p>
@@ -534,7 +534,7 @@ <h3 class="callout-title">Create and run a new Task that runs the RDA helper and
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select Manage Tasks</li>
@@ -568,7 +568,7 @@ <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor2" aria-expanded="false" aria-controls="collapseInstructor2">
   <h3 class="accordion-header" id="headingInstructor2">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor2" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor2" aria-labelledby="headingInstructor2">
+<div id="collapseInstructor2" class="accordion-collapse collapse" aria-labelledby="headingInstructor2" data-bs-parent="#accordionInstructor2">
 <div class="accordion-body">
 <p>Note: If learners need instructions on deleting their existing
 proxies for the next challenge, suggest they use a find and replace, for
@@ -605,7 +605,7 @@ <h3 class="callout-title">Add a proxy to the <code>856 40$u</code> in
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal"><li>Go to Tools in the upper menu in the MarcEditor</li>
 <li>Select Manage Tasks</li>
diff --git a/instructor/aio.html b/instructor/aio.html
index 69107fa..2a855d0 100644
--- a/instructor/aio.html
+++ b/instructor/aio.html
@@ -622,7 +622,7 @@ <h3 class="card-title">Objectives</h3>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: A number of differences have been noted in the Top Level Menu
 design and features for Mac users in this lesson: - Help is in the top
@@ -714,7 +714,7 @@ <h3 class="callout-title">Name three other tools or features that can be changed
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Click on the gear icon in the main window or go to Tools →
@@ -1138,7 +1138,7 @@ <h3 class="callout-title">Behavior when you reset your preferences and other pop
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: Some preference updates will force MarcEdit to restart and
 others will not. Also note that in order for some preference changes to
@@ -2280,7 +2280,7 @@ <h3 class="callout-title">Use the Build New Field to add a proxy to the
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools → Build New Field</li>
@@ -2381,7 +2381,7 @@ <h3 class="callout-title">Run the RDA Helper on your MARC data</h3>
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
@@ -2593,7 +2593,7 @@ <h3 class="card-title">Objectives</h3>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor1" aria-expanded="false" aria-controls="collapseInstructor1">
   <h3 class="accordion-header" id="headingInstructor1">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor1" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor1" aria-labelledby="headingInstructor1">
+<div id="collapseInstructor1" class="accordion-collapse collapse" aria-labelledby="headingInstructor1" data-bs-parent="#accordionInstructor1">
 <div class="accordion-body">
 <p>Note: “Task Actions” and “Manage Existing Tasks” menu options are
 different on a Mac.</p>
@@ -2654,7 +2654,7 @@ <h3 class="callout-title">Create and run a new Task that runs the RDA helper and
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution1" aria-expanded="false" aria-controls="collapseSolution1">
   <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 </button>
-<div id="collapseSolution1" class="accordion-collapse collapse" data-bs-parent="#accordionSolution1" aria-labelledby="headingSolution1">
+<div id="collapseSolution1" class="accordion-collapse collapse" aria-labelledby="headingSolution1" data-bs-parent="#accordionSolution1">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
@@ -2692,7 +2692,7 @@ <h4 class="accordion-header" id="headingSolution1"> Show me the solution </h4>
 <button class="accordion-button instructor-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseInstructor2" aria-expanded="false" aria-controls="collapseInstructor2">
   <h3 class="accordion-header" id="headingInstructor2">  <div class="note-square"><i aria-hidden="true" class="callout-icon" data-feather="edit-2"></i></div> Instructor Note </h3>
 </button>
-<div id="collapseInstructor2" class="accordion-collapse collapse" data-bs-parent="#accordionInstructor2" aria-labelledby="headingInstructor2">
+<div id="collapseInstructor2" class="accordion-collapse collapse" aria-labelledby="headingInstructor2" data-bs-parent="#accordionInstructor2">
 <div class="accordion-body">
 <p>Note: If learners need instructions on deleting their existing
 proxies for the next challenge, suggest they use a find and replace, for
@@ -2733,7 +2733,7 @@ <h3 class="callout-title">Add a proxy to the <code>856 40$u</code> in
 <button class="accordion-button solution-button collapsed" type="button" data-bs-toggle="collapse" data-bs-target="#collapseSolution2" aria-expanded="false" aria-controls="collapseSolution2">
   <h4 class="accordion-header" id="headingSolution2"> Show me the solution </h4>
 </button>
-<div id="collapseSolution2" class="accordion-collapse collapse" data-bs-parent="#accordionSolution2" aria-labelledby="headingSolution2">
+<div id="collapseSolution2" class="accordion-collapse collapse" aria-labelledby="headingSolution2" data-bs-parent="#accordionSolution2">
 <div class="accordion-body">
 <ol style="list-style-type: decimal">
 <li>Go to Tools in the upper menu in the MarcEditor</li>
diff --git a/instructor/index.html b/instructor/index.html
index 4bf11ed..be44807 100644
--- a/instructor/index.html
+++ b/instructor/index.html
@@ -361,7 +361,8 @@ <h2 class="accordion-header" id="flush-headingTwelve">
 <div id="prerequisites" class="callout-inner">
 <h3 class="callout-title">Prerequisites</h3>
 <div class="callout-content">
-<p>This lesson requires a basic knowledge of the MARC21 standard.</p>
+<p>This lesson requires a <a href="https://www.loc.gov/marc/96principl.html" class="external-link">basic knowledge</a> of
+the <a href="https://www.loc.gov/marc/" class="external-link">MARC21 standard</a>.</p>
 </div>
 </div>
 </div>
diff --git a/md5sum.txt b/md5sum.txt
index 173e0e3..b1e6338 100644
--- a/md5sum.txt
+++ b/md5sum.txt
@@ -2,7 +2,7 @@
 "CODE_OF_CONDUCT.md" "c93c83c630db2fe2462240bf72552548" "site/built/CODE_OF_CONDUCT.md" "2023-04-25"
 "LICENSE.md" "b24ebbb41b14ca25cf6b8216dda83e5f" "site/built/LICENSE.md" "2023-04-25"
 "config.yaml" "b99ead2aa809c42e1a1356013468889e" "site/built/config.yaml" "2024-09-19"
-"index.md" "cfdf64fcd2eb835be0b6137361b16f0b" "site/built/index.md" "2023-05-02"
+"index.md" "c516f7a4aaae1ab5d92d56b97134b02c" "site/built/index.md" "2024-10-24"
 "episodes/01-introduction.md" "ec7862eb38661b11163ce6e74ec94007" "site/built/01-introduction.md" "2023-04-25"
 "episodes/02-top-level-menu-features.md" "51bb88a2f3b2f1e0a463af05ce021307" "site/built/02-top-level-menu-features.md" "2024-08-26"
 "episodes/03-working-with-MARC-files.md" "c84fccc186f8cdee8430ad14d5a515ad" "site/built/03-working-with-MARC-files.md" "2024-08-26"