1. Brelot, M.: Étude des fonctions sousharmoniques au voisinage d’un point. Actualités Scientifiques et Industrielles. 139. (Exposés Math. publiés à la mémoire de Jacques Herbrand. III). Hermann & Cie, Paris, 55 p. (1934)
2. Cheng, S.Y., Yau, S.-T.: Differential equations on Riemannian manifolds and their geometric applications. Commun. Pure Appl. Math. 28, 333–354 (1975)
3. Duren, P., Herbig, A.-K., Khavinson, D.: Robert Jentzsch, mathematician and poet. Math. Intell. 30(3), 18–24 (2008)
4. Duren, P., Herbig, A.-K., Khavinson, D.: Robert Jentzsch: mathematician and poet. Mitt. Dtsch. Math.-Ver. 16(4), 233–240 (2008)
5. Evans, L.C.: Partial Differential Equations, vol. 19 of Graduate Studies in Mathematics. American Mathematical Society, Providence (1998)