If your citation is a book, use Franklin, the Library catalog. Franklin will help you find the library in which the book is located, and the call number.
Other important resources for finding books:
If you have a complete article citation, or even just a journal title, you can use the PennText article finder on the Library homepage.
If we do not have access to a book or journal article in any format, use interlibrary loan to request a copy from another library
Book citations generally show a publisher and a city of publication. Book chapters will include the title of the chapter as well as the name of the book.
Article citations have a journal/periodical title in addition to the article title. They will usually also show a volume and issue number, and may show a day and month.
This document suggests a good method of crafting effective keyword searches: