... On the number of positive solutions of a nonlinear algebraic system. Linear Algebra Appl. 422(2-3),404–421 (2007). doi:10.1016/j.laa.2006.10.02613. Ma, RY, Ma, HL: Positive solutions for nonlinear ... Equations 2012, 2012:3http://www.advancesindifferenceequations.com/content/2012/1/3Page 4 of 10RESEARCH Open Access Existence of positive solutions to discrete second-order boundary value problems ... doi:10.1016/j.amc.2009.06.0425. Ma, RY, Xu, J, Han, XL: Global bifurcation of positive solutions of a second-order periodic boundary value problems withindefinite weight. Nonlinear Anal: TMA. 71, 2119–2125 (2009). doi:10.1016/j.na.2009.01.0466....