You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Patent retrieval: a literature review 
Chapter Title:  TREC-CHEM collections 
1. Abstract of Cited Paper (BIB001):  Abstract : TREC 2009 was the first year of the Chemical IR Track, which focuses on evaluation of search techniques for discovery of digitally stored information on chemical patents and academic journal articles. The track included two tasks: Prior Art (PA) and Technical Survey (TS) tasks. This paper describes how we designed the two tasks and presents the official results of eight participating groups.

Literature Review:
The TREC-CHEM track was organized to motivate large-scale research on chemical datasets, especially chemical patent retrieval BIB001 . TREC-CHEM 2009: this collection was created as a test collection for two tasks BIB001 : (1) technology survey, and (2) prior art search. Eighteen topics were provided for the technology survey task where relevance judgments were obtained from experts and chemistry graduate students. For the prior art search, 1000 patents were provided as test topics where relevance judgments were collected from the citations of topic patents as well as their family members. TREC-CHEM 2011: this collection was created for the same two tasks as in previous TREC-CHEM tracks besides a new chemical image recognition task. The technology survey task topics were biomedical and pharmaceutical patents BIB002 .