Coolidge, J. L. (1939). "A Historically Interesting Formula for the Area of a Quadrilateral". The American Mathematical Monthly. 46 (6): 345–347. doi:10.2307/2302891. JSTOR2302891.
jstor.org
Coolidge, J. L. (1939). "A Historically Interesting Formula for the Area of a Quadrilateral". The American Mathematical Monthly. 46 (6): 345–347. doi:10.2307/2302891. JSTOR2302891.
upit.ro
matinf.upit.ro
E. A. José García, Two Identities and their Consequences, MATINF, 6 (2020) 5-11. [1]