General approach to regions of variability via subordination of harmonic mappings. Chen, Sh., Ponnusamy, S., Wang, X. (2009) International Journal of Mathematics and Mathematical Sciences
Generators of the Space of Bounded Biharmonic Functions. Leo Sario, Cecilia Wang (1972) Mathematische Zeitschrift
Growth properties of subharmonic functions in the unit disk Shinji Yamashita (1988) Annali della Scuola Normale Superiore di Pisa - Classe di Scienze