Harmonic Functions of Polynomial Growth on Certain Complete Manifolds. T. Christiansen, M. Zworski (1996) Geometric and functional analysis
Harnack inequality for the Schrödinger problem relative to strongly local Riemannian p -homogeneous forms with a potential in the Kato class. Biroli, Marco, Marchi, Silvana (2007) Boundary Value Problems [electronic only]
Heat kernel bounds for higher order elliptic operators E. Brian Davies (1995) Journées équations aux dérivées partielles