“…Nevertheless, the problem of describing the commutant of a given Toeplitz operator, i.e., the set of all Toeplitz operators that commute (in a sense of composition) with it, is still far from being totally solved. Almost nothing is known to us about when T f T g = T g T f for "general symbols" f and g. See [1,2,3,4,6,7,9,10,12,14,15] to know more about the commuting problem of Toeplitz operators on L 2 a (D) and the answers obtained so far for certain classes of symbols.…”