1. N. Arcozzi, L p estimates for systems of conjugate harmonic functions. Complex analysis and differential equations (Uppsala, 1997), Acta Univ. Upsaliensis Skr. Uppsala Univ. C Organ. Hist. 64 (1999), 61-68.
2. Avetisyan K., Gürlebeck K., Sprössig W.: Harmonic conjugates in weighted Bergman spaces of quaternion-valued functions. Comput. Methods Funct. Theory 9, 593–608 (2009)
3. K. Avetisyan, K.Gürlebeck, J. Morais, On 3D Riesz systems of harmonic conjugates. 9th Int. Conf. Math. Problems in Engineering, Aerospace and Sciences: ICNPAA, Vienna, 2012 AIP Conference Proceedings 1493 (2012), 441–445.
4. Brackx F., Delanghe R.: On harmonic potential fields and the structure of monogenic functions. Z. Anal. Anwendungen 22, 261–273 (2003)
5. F. Brackx, R. Delanghe and F. Sommen, Clifford analysis. Research Notes in Mathematics. 76. Boston - London - Melbourne: Pitman Advanced Publishing Program, 1982.