Dissertation Abstracts, Dissertation Abstracts International (DAI) or the ProQuest Dissertations and Theses (PQDT) database is a bibliography of American (and international) dissertations published by University Microfilms International (UMI) / ProQuest, Ann Arbor, since 1938. UMI has had an agitated life and the bibliographical data have often shifted owner and name, and therefore appears under different labels. It covers doctoral dissertations accepted at an accredited American institution since 1861. Selected Masters theses have been included since 1962; since 1988, the database includes citations for dissertations from 50 British universities that are available at The British Document Supply Centre. Besides it covers a limited number of dissertations from the rest of the world.