Euclid's Elements, Book I, Definitions 11 and 12

The definitions of Book 3 in Euclid's Elements.

Are all of Euclid's propositions necessary? - Quora

3D in the 18th century: John Cowley's appendix to Euclid's

Euclid's Elements - Wikipedia

Euclid's Elements, Book XII

Euclid's Elements - Wikipedia

Euclid's Elements - Wikiquote

Euclid's Elements - 300BC Volume 1-9, PDF, Triangle

Euclid's Elements Book ii Proposition 4.

Finishing the work of Oliver Byrne and completing with his style - the thirteen books of Euclid's Elements.

Euclid's Elements. Completing Oliver Byrne's work