I'm one-third of the way working through Manning and Schuetze www.amazon.com/Foundations-Statistical-Natural-Language-Processing/dp/0262133601, so when I saw Latent Dirichlet Allocation as the top ranked paper I headed straight to the index to see what they said about it, and discovered it was not referenced. Turns out the publication date of this paper is 2003. I knew this field was fast moving, so I've just added the first paper I have to read after I get through this book.

NLP is insanely fast-moving. Especially the machine learning side of things (like the EMNLP conference), proceedings this year have very little overlap from even 7 or 8 years ago.