« It Is not certain just what the terms alang-jabr and muqabalah mean, but the usual interpretation is similar to that implied in the translation above. The word alang-jabr presumably meant something like "restoration" or "completion" and seems to refer to the transposition of subtracted terms to the other side http://pandora.nla.gov.au/external.html?link=https://nl.wikipedia.org/wiki/Kwaliteit