Added reference cards

Author: spors

index.ipynb

@@ -6,7 +6,7 @@
    "source": [
     "# Digital Signal Processing\n",
     "\n",
-    "This collection contains the lecture notes to the masters course [Digital Signal Processing](http://www.int.uni-rostock.de/Digitale-Signalverarbeitung.48.0.html), [Institute of Communications Engineering](http://www.int.uni-rostock.de/), Universität Rostock read by [Sascha Spors](http://www.int.uni-rostock.de/Staff-Info.23+B6JmNIYXNoPWUxOTliMTNjY2U2MDcyZjJiZTI0YTc4MmFkYTE5NjQzJnR4X2pwc3RhZmZfcGkxJTVCYmFja0lkJTVEPTMmdHhfanBzdGFmZl9waTElNUJzaG93VWlkJTVEPTExMQ__.0.html). The notes are provided in the form of [jupyter](https://jupyter.org/) notebooks using IPython 3."
+    "This collection contains the lecture notes to the masters course [Digital Signal Processing](http://www.int.uni-rostock.de/Digitale-Signalverarbeitung.48.0.html), [Institute of Communications Engineering](http://www.int.uni-rostock.de/), Universität Rostock read by [Sascha Spors](http://www.int.uni-rostock.de/Staff-Info.23+B6JmNIYXNoPWUxOTliMTNjY2U2MDcyZjJiZTI0YTc4MmFkYTE5NjQzJnR4X2pwc3RhZmZfcGkxJTVCYmFja0lkJTVEPTMmdHhfanBzdGFmZl9waTElNUJzaG93VWlkJTVEPTExMQ__.0.html). The notes are provided as [Jupyter](https://jupyter.org/) notebooks using IPython 3 as Open Educational Resource. Feel free to [contact me](<mailto:[email protected]>) if you have questions or suggestions."
    ]
   },
   {
@@ -15,10 +15,11 @@
    "source": [
     "## Table of Contents\n",
     "\n",
-    "The contents of the notebooks are under heavy development. New units will be added throughout the winter 2015/16. Feel free to [contact me](<mailto:[email protected]>) if you find errors, or have questions and suggestions.\n",
-    "\n",
     "#### 0. Introduction\n",
     "\n",
+    "* [Reference Card Discrete Signals and Systems](reference_cards/RC_discrete_signals_and_systems.pdf)\n",
+    "* [Reference Card Random Signals and LTI Systems](reference_cards/RC_random_signals_and_LTI_systems.pdf)\n",
+    "\n",
     "#### 1. Spectral Analysis of Deterministic Signals\n",
     "\n",
     "* [The Leakage-Effect](spectral_analysis_deterministic_signals/leakage_effect.ipynb)\n",