"The List itself is not exhaustive, nor is it meant to be. For the subjects represented all practically useful 'see' (x) references and 'see also' (sa) references have been added but not all of them need to be used. However, it seems desirable to make them available particularly for the cataloger whose experience has been somewhat limited. A few international law, comparative law and foreign law subjects have been included because they seem to be needed regardless of the size of the collection. (...) In addition a limited number of non-legal subjects are included not only because of the fairly broad scope of the collection at the Northwestern University Law School but because to an increasing extent legal collections are including materials in related areas. Among such additional headings are the following: Biology, Eugenics, Heredity, Logic, Mathematics, Physics, Thought and thinking, etc."