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:  Patent retrieval tasks 
1. Abstract of Cited Paper (BIB001):  In this paper we describe our participation in the 2010 CLEF-IP Prior Art Retrieval task where we examined the impact of information in dierent sections of patent documents, namely the title, abstract, claims, description and IPC-R sections, on the retrieval and re-ranking of patent documents. Using a standard bag-of-words approach in Lemur we found that the IPC-R sections are the most informative for patent retrieval. We then performed a re-ranking of the retrieved documents using a Logistic Regression Model, trained on the retrieved documents in the training set. We found indications that the information contained in the text sections of the patent document can contribute to a better ranking of the retrieved documents. The ocial results have shown that among the nine groups that participated in the Prior Art Retrieval task we achieved the eigth rank in terms of both Mean Average Precision (MAP) and Recall. 
2. Abstract of Cited Paper (BIB002):  There is a growing literature that aims at assessing the private value of knowledge assets and patents. It has been shown that patents and their quality as measured by citations received by future patents contribute significantly to the market value of firms beyond their R&D stocks. This paper goes one step further and distinguishes between different types of forward citations patents can receive at the European Patent Office. While a patent can be cited as non-infringing state of the art, it can also be cited because it threatens the novelty of patent applications ('blocking citations'). Empirical results from a market value model for a sample of large, R&D-intensive U.S., European and Japanese firms show that patents frequently cited as blocking references have a higher economic value for their owners than patents cited for nonblocking reasons. This finding adds to the patent value literature by showing that different types of patent citations carry different information on the economic value of patents. The result further suggests that the total number of forward citations can be an imprecise measure of patent value. 
3. Abstract of Cited Paper (BIB003):  Document search on PubMed, the pre-eminent database for biomedical literature, relies on the annotation of its documents with relevant terms from the Medical Subject Headings ontology (MeSH) for improving recall through query expansion. Patent documents are another important information source, though they are considerably less accessible. One option to expand patent search beyond pure keywords is the inclusion of classification information: Since every patent is assigned at least one class code, it should be possible for these assignments to be automatically used in a similar way as the MeSH annotations in PubMed. In order to develop a system for this task, it is necessary to have a good understanding of the properties of both classification systems. This report describes our comparative analysis of MeSH and the main patent classification system, the International Patent Classification (IPC). We investigate the hierarchical structures as well as the properties of the terms/classes respectively, and we compare the assignment of IPC codes to patents with the annotation of PubMed documents with MeSH terms. Our analysis shows a strong structural similarity of the hierarchies, but significant differences of terms and annotations. The low number of IPC class assignments and the lack of occurrences of class labels in patent texts imply that current patent search is severely limited. To overcome these limits, we evaluate a method for the automated assignment of additional classes to patent documents, and we propose a system for guided patent search based on the use of class co-occurrence information and external resources.

Literature Review:
The goal of PR is to retrieve relevant patent documents to a given search request (query). This request can take different forms such as a sequence of keywords, a memo, or a complete text document (e.g., a patent application). The purpose of this task is manifold, for example: -Retrieve related patents to a given patent application in order to gather related work or invalidate one or more of its claims. -Explore patent filing activity under specific technology. -Explore the competitive landscape of a given company by looking at other companies filing patents similar to the given company patents. Because of these multiple objectives, various PR tasks were proposed to fulfill each objective, and multiple datasets were provided depending on the given task. Prior art search is the main theme of the CLEF-IP and NTCIR tracks. The importance of this task stems from the requirement by all patent offices that filed patents must constitute novel, non-obvious, and non-abstract ideas. Therefore, an important activity through the patent life cycle is to thoroughly ensure that no earlier published patent or material describing the prescribed ideas exist. The task can be defined as follows: Problem: given a patent application X, retrieve all related documents to X Prior art search is a total-recall task, BIB001 therefore it demonstrates several challenges. Search coverage is one of the main challenges, because it is required to cover all previously published material (patent or non-patent literature) in all forms (electronic or printed) which is infeasible. Another major challenge is the need to search through materials written in different languages. Last but not least, traditional IR methods perform poorly when confronted with the patent prior art search task. Mainly because the patent language is full of jargon and user-defined terminology. Inventors intentionally tend to use different vocabularies to express same or similar ideas in order to establish the novelty of their work. Prior art search is performed at different stages of the patent life cycle, by different stakeholders, for various purposes, and for limited period of time. Understanding the reallife practices of patent professionals is critical to better satisfy their information need  . In other words, the search scenario depends on when it is done, by whom, and for what reason(s). Table 2 shows these various scenarios which are detailed below. Related work search: during the pre-grant stage, inventors and prosecutors run related work search to retrieve all relevant work to the invention. Moreover, some patent offices Table 2 Scenarios of patent prior art search Patentability search: during the examination stage, patent examiners perform patentability search in order to ensure that the proposed ideas are novel, non-obvious, and non-abstract. The output of this task would be a search report with all retrieved relevant publications. In this report, each entry will have a special code indicating whether it is just a related publication or novelty breaking one. Examiners would also specify which passages or figures in retrieved publications constitute relevancy. Depending on the search findings, the patent office might grant, reject, or ask the applicant to modify the patent application. Patentability search is also performed by patent prosecutors as a sanity check. Although this task should be of equal interest to prosecutors who file the patent application as it is to examiners, prosecutors often do not dig deep searching for relevant publications, and delegate finding relevant prior work to examiners in order to save costs. Infringement search: this task, also called product clearance search, aims to ensure whether an existing or a proposed product is infringing any published patent claim(s). Patent owners require that type search to find out whether a third party has a product with features that are within the scope of one or more claims of their patents. If so, they might either sue or negotiate a license with that infringing party. Investors and R&D managers, on the other hand, require that type of search to ensure newly proposed product(s) are not infringing a published patent claim(s) and investment in such products would be lucrative. The scope of search in this case would be limited to patent and the copyrighted literature only. Deep understanding and correct interpretation of patent claims are imperative for building the correct correspondence between product features and claims in order to establish or dismiss infringement. Freedom to operate search: this PR task extends beyond infringement search. Here, investors and R&D managers not only need to make sure that proposed products do not infringe an existing patent or copyrighted material, but also to ensure they have the freedom to file patents on these products without worrying about previous prior art that might invalidate such inventions. Another objective of freedom to operate search is to make better investment decisions and R&D plans according to existing prior art. Invalidity search: as patents guarantee monopoly rights to their owners on the economic value of granted inventions, companies and other parties usually monitor granted patents of their competitors or pertaining to their technology landscape to ensure competitive superiority. Therefore, invalidity search is performed to find published material that was missed by the patent office during patentability search. Invalidity search is also considered as the first line of defense when a party is confronted with patent infringement lawsuit. Again published material might include patent or non-patent literature such as books, news articles, academic periodicals. After finding such validity breaking material, a third party might file a post-grant (opposition) procedure depending on the patent office policies. For example, the USPTO provides procedures such as reexamination, inter-partes Review, BIB003 and post-grant review BIB002 in front of the Patent Trial and Appeal Board BIB004