(Ifrah 2000, p. 346): "The measure of the genius of Indian civilisation, to which we owe our modern (number) system, is all the greater in that it was the only one in all history to have achieved this triumph. Some cultures succeeded, earlier than the Indian, in discovering one or at best two of the characteristics of this intellectual feat. But none of them managed to bring together into a complete and coherent system the necessary and sufficient conditions for a number-system with the same potential as our own." Ifrah, Georges (2000), written at New York, A Universal History of Numbers: From Prehistory to Computers, Wiley, 658 pages, ISBN 0471393401, <http://www.amazon.com/Universal-History-Numbers-Prehistory-Invention/dp/0471393401/>.
(Bourbaki 1998, p. 49): "On this point, the Hindus are already conscious of the interpretation that negative numbers must have in certain cases (a debt in a commercial problem, for instance). In the following centuries, as there is a diffusion into the West (by intermediary of the Arabs) of the methods and results of Greek and Hindu mathematics, one becomes more used to the handling of these numbers, and one begins to have other "representation" for them which are geometric or dynamic." Bourbaki, Nicolas (1998), written at Berlin, Heidelberg, and New York, Elements of the History of Mathematics, Springer-Verlag, 301 pages, ISBN 3540647678, <http://www.amazon.com/Elements-History-Mathematics-Nicolas-Bourbaki/dp/3540647678/>.
"algebra" 2007. Britannica Concise Encyclopedia. Encyclopædia Britannica Online. 16 May 2007. Quote: "A full-fledged decimal, positional system certainly existed in India by the 9th century (AD), yet many of its central ideas had been transmitted well before that time to China and the Islamic world. Indian arithmetic, moreover, developed consistent and correct rules for operating with positive and negative numbers and for treating zero like any other number, even in problematic contexts such as division. Several hundred years passed before European mathematicians fully integrated such ideas into the developing discipline of algebra."
(Pingree 2003, p. 45) Quote: "Geometry, and its branch trigonometry, was the mathematics Indian astronomers used most frequently. In fact, the Indian astronomers in the third or fourth century, using a pre-Ptolemaic Greek table of chords, produced tables of sines and versines, from which it was trivial to derive cosines. This new system of trigonometry, produced in India, was transmitted to the Arabs in the late eighth century and by them, in an expanded form, to the Latin West and the Byzantine East in the twelfth century." Pingree, David (2003), "The logic of non-Western science: mathematical discoveries in medieval India", Daedalus132 (4): 45-54, <http://www.questia.com/googleScholar.qst?docId=5007155010>.