Equation Icon  a 0 = \~/ \~/ af, (5) 0 = \~/ a\ ~/ ay + \~/ a(t ab \~/ by), (6) 1 1 1 Gab = \~/ af \~/ bf - -- \~/ sf \~/ sfgab + \~/ ay \~/ by - - \~/ sy \~/ sygab - -t rs \~/ ry \~/ sygab. (7) 2 2 2