Han, Y., J. Li, and C.-C. Lin. “Criterions of the L^2 Boundedness and Sharp Endpoint Estimates for Singular Integral Operators on Product Spaces of Homogeneous type ”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, vol. 16, no. 3, Sept. 2016, pp. 845-07, doi:10.2422/2036-2145.201411_002.