Homework Statement
Given this three operators in the same orthonormal base, [H]=[{0,1,0},{1,0,0},{0,0,1}], [A]=[{1,0,0},{0,1,0},{0,0,1}] and =[{1,1,1},{1,1,1},{1,1,1}], tell which of these observables form a complete set of compatible observables:
[H], [H,A], [H,B] or [H,A,B]
Homework...