BLIZNIKAS, V. Über die Geometrie des quasilinearischen Systems Partiellen Differentialgleichungen erster Ordnung. Lithuanian Mathematical Journal, [S. l.], v. 9, n. 2, p. 205–210, 1969. DOI: 10.15388/LMJ.1969.20748. Disponível em: https://www.journals.vu.lt/LMJ/article/view/20748.. Acesso em: 19 jul. 2024.