diff --git a/controllers/ApiController.php b/controllers/ApiController.php
index b02bb4e0..4e343bf0 100644
--- a/controllers/ApiController.php
+++ b/controllers/ApiController.php
@@ -482,7 +482,7 @@ public function init($extra) {
 		
 		// Sorting by Item Type or Added By currently require writing to shard tables, so don't
 		// send those to the read replicas
-		if ($this->queryParams['sort'] == 'itemType' || $this->queryParams['sort'] == 'addedBy') {
+		if ($this->queryParams['sort'] == 'itemType' || $this->queryParams['sort'] == 'addedBy' || $this->queryParams['sort'] == 'editedBy') {
 			Zotero_DB::readOnly(false);
 		}
 		
diff --git a/model/API.inc.php b/model/API.inc.php
index 863104a3..0a015394 100644
--- a/model/API.inc.php
+++ b/model/API.inc.php
@@ -397,6 +397,7 @@ public static function parseQueryParams($queryString, $action, $singleObject, $a
 					//case 'numChildren':
 					
 					case 'addedBy':
+					case 'editedBy':
 					case 'numItems':
 					case 'serverDateModified':
 					
diff --git a/model/Items.inc.php b/model/Items.inc.php
index df08d0c6..9ab05e95 100644
--- a/model/Items.inc.php
+++ b/model/Items.inc.php
@@ -274,13 +274,15 @@ public static function search($libraryID, $onlyTopLevel = false, array $params =
 					// Join temp table to query
 					$sql .= "JOIN tmpItemTypeNames TITN ON (TITN.itemTypeID=$itemTypeIDSelector) ";
 					break;
-				
+
+				case 'editedBy':
 				case 'addedBy':
 					$isGroup = Zotero_Libraries::getType($libraryID) == 'group';
+					$userParameter = $params['sort'] == "editedBy" ? 'lastModifiedByUserID' : 'createdByUserID';
 					if ($isGroup) {
-						$sql2 = "SELECT DISTINCT createdByUserID FROM items
+						$sql2 = "SELECT DISTINCT $userParameter FROM items
 								JOIN groupItems USING (itemID) WHERE
-								createdByUserID IS NOT NULL AND ";
+								$userParameter IS NOT NULL AND ";
 						if ($itemIDs) {
 							$sql2 .= "itemID IN ("
 									. implode(', ', array_fill(0, sizeOf($itemIDs), '?'))
@@ -307,7 +309,7 @@ public static function search($libraryID, $onlyTopLevel = false, array $params =
 							
 							// Join temp table to query
 							$sql .= "LEFT JOIN groupItems GI ON (GI.itemID=I.itemID)
-									LEFT JOIN tmpCreatedByUsers TCBU ON (TCBU.userID=GI.createdByUserID) ";
+									LEFT JOIN tmpCreatedByUsers TCBU ON (TCBU.userID=GI.$userParameter) ";
 						}
 					}
 					break;
@@ -550,6 +552,7 @@ public static function search($libraryID, $onlyTopLevel = false, array $params =
 					$orderSQL = "$sortTable.value";
 					break;
 				
+				case 'editedBy':	
 				case 'addedBy':
 					if ($isGroup && $createdByUserIDs) {
 						$orderSQL = "TCBU.username";
@@ -2574,6 +2577,16 @@ private static function loadItems($libraryID, $itemIDs=array()) {
 			}
 		}
 	}
+
+	public static function getItemsWithoutCollection($libraryID) {
+		$sql = "SELECT items.itemID
+		FROM items
+		LEFT JOIN collectionItems ON items.itemID = collectionItems.itemID
+		WHERE collectionItems.collectionID IS NULL
+		AND items.libraryID = ?;";
+		$items = Zotero_DB::columnQuery($sql, $libraryID, Zotero_Shards::getByLibraryID($libraryID));
+		return $items;
+	}
 	
 	
 	public static function getSortTitle($title) {