Now Ian Steer posts Who discovered Universe expansion?:
Swedish astronomer, Knut Lundmark, were much more advanced than formerly appreciated. ...I credit Lemaitre because he was the first to publish a cosmological model with red-shift proportional to distance, and to publish observational data to back it up. I don't know how Hubble stole the credit.
Lundmark was the first person to find observational evidence for expansion, in 1924 — three years before Lemaître and five years before Hubble. Lundmark’s extragalactic distance estimates were far more accurate than Hubble’s, consistent with an expansion rate (Hubble constant) that was within 1% of the best measurements today. ...
Hubble’s research in 1929 yielded a value for the Hubble constant that was inaccurate by almost an order of magnitude. It was adopted because it was derived from multiple methods — including one still in use (brightest stars) — and was cross-checked with multiple galaxies with distances based on proven Cepheid star variables.