Authors:

To 'know Thyself' is considered quite an accomplishment.

L. Frank Baum (2008). “7 Books in 1: L. Frank Baum's "Oz" Series, Volume 1 of 2. the Wonderful Wizard of Oz, the Marvelous Land of Oz, Ozma of Oz, Dorothy”, p.183, Shoes & Ships & Sealing Wax
To 'know Thyself' is considered quite an accomplishment.