01161nas a2200157   4500008004100000020001400041245007800055210006900133260001500202300001200217520066800229100002200897700001900919700001900938856004600957       2021                        eng d  a0219-199700aNon-well-ordered lower and upper solutions for semilinear systems of PDEs0 aNonwellordered lower and upper solutions for semilinear systems   c2021/08/27  a21500803 a<p>We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.We prove existence results for systems of boundary value problems involving elliptic second-order differential operators. The assumptions involve lower and upper solutions, which may be either well-ordered, or not at all. The results are stated in an abstract framework, and can be translated also for systems of parabolic type.</p>1 aFonda, Alessandro1 aKlun, Giuliano1 aSfecci, Andrea  uhttps://doi.org/10.1142/S0219199721500802