Timeline of knowledge about the interstellar and intergalactic medium (English Wikipedia)

Ewen, H. I.; Purcell, E. M. (September 1951), "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec.", Nature, 168 (4270): 356, Bibcode:1951Natur.168..356E, doi:10.1038/168356a0, S2CID 27595927
Gunn, James E.; Peterson, Bruce A. (November 1965), "On the Density of Neutral Hydrogen in Intergalactic Space", Astrophysical Journal, 142: 1633–1641, Bibcode:1965ApJ...142.1633G, doi:10.1086/148444
Wilson, R. W.; Jefferts, K. B.; Penzias, A. A. (July 1970), "Carbon Monoxide in the Orion Nebula", Astrophysical Journal, 161: L43, Bibcode:1970ApJ...161L..43W, doi:10.1086/180567

harvard.edu (Global: 18^th place; English: 17^th place)

Ewen, H. I.; Purcell, E. M. (September 1951), "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec.", Nature, 168 (4270): 356, Bibcode:1951Natur.168..356E, doi:10.1038/168356a0, S2CID 27595927
Gunn, James E.; Peterson, Bruce A. (November 1965), "On the Density of Neutral Hydrogen in Intergalactic Space", Astrophysical Journal, 142: 1633–1641, Bibcode:1965ApJ...142.1633G, doi:10.1086/148444
Wilson, R. W.; Jefferts, K. B.; Penzias, A. A. (July 1970), "Carbon Monoxide in the Orion Nebula", Astrophysical Journal, 161: L43, Bibcode:1970ApJ...161L..43W, doi:10.1086/180567

Ewen, H. I.; Purcell, E. M. (September 1951), "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec.", Nature, 168 (4270): 356, Bibcode:1951Natur.168..356E, doi:10.1038/168356a0, S2CID 27595927