Combinations

Coupling

[ ( π 1 ± π 2 ± ) i ( π 1 ± π 2 ± ) j ]

coupling of I˚ degree

{ ( π 1 ± π 2 ± ) i [ ( π 1 ± π 2 ± ) j ( π 1 ± π 2 ± ) k ] }

coupling of II˚ degree

[ ( π 1 ± π 2 ± ) i ( π 1 ± π 2 ± ) j ] [ ( π 1 ± π 2 ± ) k ( π 1 ± π 2 ± ) r ]

coupling of III˚ degree

{ ( π 1 ± π 2 ± ) i [ ( π 1 ± π 2 ± ) j ( π 1 ± π 2 ± ) k ( π 1 ± π 2 ± ) r ] }

coupling of IV˚ degree