This month several articles dedicated for googology were published in Wikipedia (russian and ukrainian)
Notice, in those articles reliable sources for definition of googology are listed. Particularly,
1) Prof. Dr. Ir. Maarten Looijen. Over getallen gesproken - Talking about numbers. — Van Haren Publishing, 2016. — P. 211. — ISBN 978-94018-0028-0.
2) One Million Things: A Visual Encyclopedia. — New York, New York 10014, United States: DK Publishing, 2008. — P. 286. — ISBN 978-0-7566-3843-6.
You can use them if you want to write articles about googology in wikipedia in your native languages.