theorem :: ROBBINS4:38

for L being non empty OrthoLattStr holds
( L is Orthomodular_Lattice iff ( ( for a, b, c being Element of L holds (a "\/" b) "\/" c = (((c `) "/\" (b `)) `) "\/" a ) & ( for a, b, c being Element of L holds a "\/" b = ((a "\/" b) "/\" (a "\/" c)) "\/" ((a "\/" b) "/\" (a `)) ) & ( for a, b being Element of L holds a = a "\/" (b "/\" (b `)) ) ) )