Wilfrid Hodges (2018-05-24). "Historical Appendix: A short history of model theory". Philosophy and model theory. By Button, Tim; Walsh, Sean. p. 439. doi:10.1093/oso/9780198790396.003.0018.
"All three commentators [i.e. Vaught, van Heijenoort and Dreben] agree that both the completeness and compactness theorems were implicit in Skolem 1923...." [Dawson, J. W. (1993). "The compactness of first-order logic:from Gödel to Lindström". History and Philosophy of Logic. 14: 15–37. doi:10.1080/01445349308837208.]