FRENTZ, M.; GAROFALO, N.; GÖTMARK, E.; MUNIVE, I.; NYSTRÖM, K. Non-divergence form parabolic equations associated with non-commuting vector fields: boundary behavior of nonnegative solutions. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, [S. l.], v. 11, n. 2, p. 437-474, 2012. DOI: 10.2422/2036-2145.201007_004. Disponível em: https://journals.sns.it/index.php/annaliscienze/article/view/269. Acesso em: 10 feb. 2025.