The world of information is so vast that there is a good chance that even the most difficult sounding request can be answered. You need to specifically offer this service. Patrons are often reluctant to put you to the trouble of referring their questions. You will need to assure them that this is a standard library service and one we are glad to give. If you find time to work on it later, check with the Nebraska Library Commission's Reference Desk to find out what has already been done to avoid duplication of searching.
Many questions sound impossible.
Suppose your patron asks for directions on how to build a perpetual motion machine. You may be tempted not to refer questions like that, but give it a try anyway. Even though your patron may not, in the end, get step by step instructions, you may be able to supply a history or discussion of the issue which would be helpful. And remember that what sounds impossible to you may be really easy for those working with a larger collection. Sometimes patrons ask for something that we can't provide due to policy considerations.