General Reference
National Bibliographies
National Bibliographies are a way to search through the publication output of various countries in this region. The University of Illinois has an excellent guide to navigating these, which is provided as the first link. The Russian National Bibliographies also include map, musical, and periodical publications.
Librarian
Outside Guides to Resources
Librarians have compiled and developed guides at various institutions outside of the University of Chicago, which may be helpful to researchers here. You may not be able to access all resources listed, but many resources are freely available or also available through the University of Chicago.