Misra, U., S. K. Sahu, D. Acharya, and P. Nayak. “Approximation of Fourier Series of a Function of Lipchitz Class by Product Means”. Journal of Progressive Research in Mathematics, Vol. 4, no. 4, Aug. 2015, pp. 399-07, http://scitecresearch.com/journals/index.php/jprm/article/view/305.