... U, Classification of solutions for a system of integral equations, Comm Partial Differential Equations 30 (20 05), pp 59–65 1, 26 30 31 32 33 34 35 36 SYSTEM OF INTEGRAL EQUATIONS VIA THE METHOD ... setting, Eq (1 .3) is associated with some fourth order partial differential equation since it simply becomes 25 (−∆ )2 u = u−q 20 21 22 23 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 (1.5) ... solving systems of integral equations As far as we know, this is the first attempt to use the method of moving spheres for systems (with negative exponents) 16 17 18 19 20 21 22 23 24 25 26 27 28 ...