diff --git a/books.md b/books.md
index 541e31e..21e08f2 100644
--- a/books.md
+++ b/books.md
@@ -37,7 +37,10 @@ and Prediction](http://users.soe.ucsc.edu/~draper/draper-BMIP-dec2005.pdf)
 * [NLTK](http://www.nltk.org/book/)
 * [NLP w/ Python](http://victoria.lviv.ua/html/fl5/NaturalLanguageProcessingWithPython.pdf)
 * [Foundations of Statistical Natural Language Processing](http://nlp.stanford.edu/fsnlp/promo/)
-* [Speech and Language Processing (Second Edition)](http://www.cs.colorado.edu/~martin/SLP/Updates/1.pdf)
+
+## Information Retrieval
+
+* [An Introduction to Information Retrieval](http://nlp.stanford.edu/IR-book/pdf/irbookonlinereading.pdf)
 
 ## Neural Networks