equation icon  @fa - @af - xefae + 2xaefe + xa f + @a/\ + Eadsd = 0, (56) 1 @[cfa]- x[cefa]e + x[ca]f - -ecaeBedsd = 0, (57) 2 @fab - @(afb) + 2x(afb) + x(aefb)e- x(ab)f - hab@/\ - Eabs - B(aeeb)desd = 0, (58) 1 1 @[cfa]b- x[ac]fb + f[axc]b - hb[a@c]/\ + --ecaeBebs - -ecaeEefefbdsd = 0. (59) 2 2