Constraints on massive star formation: Cygnus OB2 was always an associationDOI: info:10.1093/mnras/stt2232v. 438639–646
Wright, Nicholas J., Parker, Richard J., Goodwin, Simon P., and Drake, Jeremy J. 2014. "Constraints on massive star formation: Cygnus OB2 was always an association." Monthly Notices of the Royal Astronomical Society, 438 639–646. https://doi.org/10.1093/mnras/stt2232.