1. Formules de cubatures mécaniques a coefficients nonnégatifs;Tchakaloff;Bull Sci. Math,1957
2. P. S. Davis. Approximate integration rules with nonnegative weights. Brown Univ. Div. of Applied Math. report. Chapt. 1 to 5.
3. E. W. Cheney and A. A. Goldstein. Newton's method for convex programming and Tchekycheff Approximation.