Use WorldCat to find materials in other libraries.
Need to request a copy of a book that's not available at Lehigh? Use Interlibrary Loan to have books sent here. You will get an email when your book is ready for pickup.
Try your luck searching the full text of books using Google Books... perhaps the book you need is out of copyright and available in its entirety online. Also the full text searching capability of Google Books might identify something useful that you can get here at Lehigh or borrow through PALCI or Interlibrary Loan (ILLiad).