Searching non-Eurasian (i.e., North American and Western European) library catalogs is extremely useful for determining what materials might be available relatively quickly via interlibrary loan.  Searching virtually all North American and Western European library catalogs at once via WorldCat is even more useful.  But researchers should keep in mind that North American and Western European collections of Eurasian materials, as impressive as they may be, are woefully incomplete compared to the great library collections of Eurasia itself, which obviously have done a much better job of collecting their own publications.  Searching Eurasian library catalogs online is an excellent way to get a sense of the full range of publications on your topic.  One of the best (and quirkiest) catalogs for this purpose is the Russian State Historical Library's Subject Catalog (Predmetnyi Katalog).  This was an effort on the part of the library's staff to provide easy access to materials on topics that did not fit neatly into the old Soviet subject classification system.  There are, for example, 15 card catalog cards about the noted prerevolutionary Russian climatologist A. I. Voeikov (1842-1916), which point the way toward journal articles, reviews, and book chapters, as well as monographs, some of them quite obscure and virtually impossible to find by any other means, as can be seen in the example below.

There are also 15 cards about the botanist and geologist Vasilii Sapozhnikov (1861-1924):