Where to start? Is WorldCat the most complete search available for Czech materials? Maybe starting with Google is really the best bet? While these are all valid approaches in particular situations, no one of them will answer all needs. Not every title in a library will be searchable through WorldCat. The reason is technical and the problem may be corrected in the future. At present libraries with large collections such as the University of Illinois or the Library of Congress have a number of records that do no have full cataloging in a "machine-readable format". Those titles are not in WorldCat making it a very good source but a source with limitations. By extension, such titles will not be in Google's book search unless the title has been scanned.
It is also important to keep in mind that the titles available in the U.S. only represent a small portion of the total publishing output from the countries of Eastern Europe and Eurasia. The catalog records from most of the libraries of our region are not available at all in WorldCat. Those that are there are current publications.
Another facet of the online sources such as WorldCat, the access in such sources may not tell you what source will best answer your needs. That is, there is no annotation, you have not seen the whole range of published material you are choosing just what happens to be available here, not necessarily the best source for your research.
So where should you start? It can be helpful to start with a few questions about your research
