Avdzhieva, Ana, Vesselin Gushev, and Geno Nikolov. 2017. “DEFINITE QUADRATURE FORMULAE OF ORDER THREE WITH EQUIDISTANT NODES”. Ann. Sofia Univ. Fac. Math. And Inf. 104 (December):155-70. https://annual.uni-sofia.bg/index.php/fmi/article/view/42.