CHUNG, L. O.; SARIO, L.; WANG, C. Harmonic and polyharmonic degeneracy. Mathematica Scandinavica, Berkeley, CA, United States, v. 40, p. 288–292, 1977. DOI: 10.7146/math.scand.a-11695. Disponível em: https://journals.msp.org/mscand/article/view/1952. Acesso em: 25 jul. 2026.