LSU's main library collection, numbering almost three million volumes, is housed in Troy H. Middleton Library on the main quadrangle of the university. It is both a general use library and a . Regional Depository Library, housing publications from the federal government, United Nations , and United States Patent and Trademark Office . The LSU Libraries belong to the Association of Research Libraries , which includes the top 113 academic libraries in the . and Canada; the Association of Southeastern Research Libraries (ASERL); LYRASIS , which is a merger of the Southeastern Library Network SOLINET with PALINET; and the Louisiana Academic Library Information Network Consortium (LALINC). LSU was among the founding members of the Louisiana Online University Information System (LOUIS) network which provides access to most academic library catalogs in the state. The LSU Libraries' subject strengths include Louisiana materials, sugar culture and technology, Southern history, agriculture, petroleum engineering, plant pathology, natural history, and various aspects of aquaculture including crawfish, wetlands research, and marine biology.