[Obo-anatomy] dbxref of a citation

[Sofia Robb]

Hello,

I am creating an obo file with definition lines that have references that cannot be found in any online database as far as I can tell. How do I format my dbxref if I have the following list of references:

OCLC:42792751 PMID:15599763 Hallez, P. (1887). Embryogénie des Dendrocoeles d’eau douce, Vol 16. 4)  Ijima, I. (1884). Untersuchungeniiber den Bau und die Entwicklungsgeschichte der stisswasser-Dendrocoelen(Tricladen). Vol Bd. 40. Le Moigne, A. (1963). Etude du developpement embryonnaire de Polycelis nigra (Turbellarie - Triclade). Bulletin de la Societe Zoologique de France 88, 403-422. Metschnikoff, E. (1883). Die embryologie von Planaria polychroa. Zeitschrift fur wissenschaftliche Zoologie 38, 331-354. PMID:19197510 Thanks! Sofia