Harvard Mining School Plat of the Observatory Grounds of Harvard University, surveyed October 1869
“Harvard Mining School Plat of the Observatory Grounds of Harvard University, surveyed October 1869”, vers 1875, Bibliothèque de l'Observatoire de Paris. Consulté le 16 avr. 2024, https://bibnum.explore.psl.eu/s/psl/ark:/18469/1htrs
