 Here's the list of sources I use to put together the How Old Is It? video book. These books, videos, and websites also represent resources you can use to do additional research into areas touched on in this video book. I used the YouTube Stanford University Cosmological Lectures 1-10 by Leonard Suskind extensively. He introduces the study of cosmology and derives the classical physics formulas that describe our expanding universe. It's the best out there. Here is the book I used extensively. The author puts it all together in a very logical order that is easy to follow. But it does have a lot of calculus-level math. And don't miss Ned Wright's Cosmological Tutorial site. It is the best site for basic information presented in a straightforward way. His frequently asked questions page is absolutely outstanding. And don't forget every video segment has a document with the text, links, music, pictures and notes located on howfarawayisit.com slash documents. The following identifies all of my sources. Thanks for watching.