Pottage,John(1974),“The mensuration of quadrilaterals and the generation of Pythagorean triads: a mathematical, heuristical and historical study with special reference to Brahmagupta's rules”,Archive for History of Exact Sciences12(4): 299–354,doi:10.1007/BF01307176,MR0465678
↑ Pottage 1974, See in particular the footnote on p.313..