Zhao et al Advances in Difference Equations 2011, 2011:10 http://www.advancesindifferenceequations.com/content/2011/1/10 RESEARCH Open Access Positive solutions for a coupled system of nonlinear differential equations of mixed fractional orders Yige Zhao1, Shurong Sun1,2*, Zhenlai Han1,3 and Wenquan Feng1 * Correspondence: sshrong@163 com School of Science, University of Jinan, Jinan 250022, Shandong, PR China Full list of author information is available at the end of the article Abstract In this article, we study the existence of positive solutions for a coupled system of nonlinear differential equations of mixed fractional orders ⎧ ⎪ −Dα+ u(t) = f (t, v(t)), < t < 1, ⎨ β0 D0+ v(t) = g(t, u(t)), < t < 1, ⎪ ⎩ u(0) = u(1) = u (0) = v(0) = v(1) = v (0) = v (1) = 0, where