equation icon  [ ] [( ) ] 0 a a 1 2 3 1 2 1 2 3 a ea dx = 1 + raa_O_ + 2r S + O(r ) du + 1 + 6-r S _O_a - 6r Sa + O(r ) d^x , (169) [ ] [ ] a a ( a a b) 1- 2 a 3 a 1- 2 a 1- 2 a 3 b ea dx = r a - w b_O_ + 2r S + O(r ) du + db - 6 r S b + 6 r S _O_b + O(r ) d^x . (170)