SKJENNEBERG, Sven. Lars Hällbom; Nitrogenase regulation and ultrastructure of heterocystous cyanobacteria; free living and in lichen symbiosis. Rangifer, Tromsø, Norway, v. 2, n. 1, p. 52, 1982. DOI: 10.7557/2.2.1.431. Disponível em: https://septentrio.uit.no/index.php/rangifer/article/view/431. Acesso em: 19 apr. 2026.