In this paper, page $6$ the authors state the following:

By Weil’s theorem $[17]$, any local algebraic group is birationally equivalent to an algebraic group.

Where

$[17]$ A.Weil. On algebraic groups of transformations. Amer. J. Math. 77, (1955), 355-391.

I would like to know if I can find that Theorem in a textbook about Algebraic Groups.

I would appreciate your help.

PS. I did ask this question in StackExchange, but I got no answer.