books.google.com - The writings of Newton, Leibniz, Pascal, Riemann, Bernoulli, and others in a comprehensive selection of 125 treatises dating from the Renaissance to the late 19th century — most unavailable elsewhere. Grouped in five sections: Number; Algebra; Geometry; Probability; and Calculus, Functions, and Quaternions. Includes...http://books.google.com/books/about/A_Source_Book_in_Mathematics.html?id=awAfO7Ff_z0C&q=variables&utm_source=gb-gplus-shareA Source Book in Mathematics