Não informado. Publications of the Allegheny Observatory of the University of Pittsburgh. University of Pittsburgh.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Publications of the Allegheny Observatory of the University of Pittsburgh. Lancaster, Pa: University of Pittsburgh.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Publications of the Allegheny Observatory of the University of Pittsburgh. University of Pittsburgh.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.