equation icon  ( )( ) pa(u) = ga ea'ub'+ ga ua' a 'eb' a a';b' a a' b a [ 1 ] [ 1 ] = aa + -rRa0b0_O_b + O(r2) ea0 + - -rRba0c_O_c + O(r2) eab , 2 ( 2 ) ( )( ) ( )( ) ¨pa(u) = ga ' ' 'ea'ub'ug'+ ga '' 2ua'ub'a 'eg'+ ea'ab' + ga 'aa' a 'eb' + ga 'ua' a 'eb' a a ;b g a [ a ;b ] g a a a b a a b a = [aa + O(r)] ea0 + aaab + O(r) eab ,