Quasihomogeneous Toeplitz operators on the harmonic Bergman space
  In this paper we study the product of Toeplitz operators on the harmonic Bergman space of the unit disk of the complex plane C. Mainly, we discuss when the product of two quasihomogeneous Toeplitz operators is also a Toeplitz operator, and when such operators commute. 
Issam Louhichi, Lova Zakariasy
math.FA math.OA