equation icon  x(1 - x)p ''+ [1 - s - ie- it - (2 - 2it)x]p '+ [it(1 - it) + c + s(s + 1)]p = in in in 2iek[- x(1- x)pin'+ (1- s + ie - it)xpin] + [e2 - iek(1 - 2s)]pin, (117)