@mastersthesis {532,
	title = {Sistemas de Ermakov generalizados, simetrias e invariantes exatos},
	year = {1998},
	school = {UFRGS},
	type = {PhD thesis},
	address = {Porto Alegre},
	attachments = {https://professor.ufrgs.br/sites/default/files/fernando-haas/files/phd_thesis.pdf},
	author = {F. Haas}
}
