Union catalogs, catalogs that list the holdings of many libraries, can offer the researcher not only a broader collection of materials but also locational options. 

• General bibliographic resources are just that, they are not limited to a specific subject
• Comprehensive subject sources will save time and effort on interdisciplinary searches but may be more time-consuming to search
• These sources include various types of media: text, audio, video, electronic
• If Google seems the best approach, try search the vernacular language version using the script of that country.  You will often find material here not indexed in the English language version of Google.  Keep other vernacular language search engines in mind as well.
• Some national library catalogs can act as subject bibliographies to a certain extent.
• If you are searching European library catalogs be sure you use the transliteration they employ.  An excellent comparative table for cyrillic is available at Transliteratsiia Russkogo Alfavita. 

Some electronic resources for vernacular materials include little or no information on their compilation. In some cases it is impossible to know who compiled an online source, how or where it was done or what chronological 

Digital resources can seem to be all-encompassing and many are extremely impressive, truly simplifing scholarly research. In general, they do not tend to have great retrospective depth though this is improving. Still, they can save you time when looking for current publications. If you are looking for older publications, your search is likely to require the use of a combination of print and online sources.

 In the left hand box there is a list of union catalogs.  These are web interfaces that allow you to search many libaries, usually in a single country, with one set of search terms.  This can be very helpful when planning your research if you are trying to determine which libraries will have the richest depositories for your research.  They can also be helpful if your library participates in International Interlibrary Loan.  This will assist your librarian in obtaining the material you need.