A trivia question about domain names.

[Ronald F. Guilmette]

Once upon a time, RFC 1035 made domain names like:

	beverly-hills.90210.com

illegal, because it disallowed domain name components that contained
nothing but digit characters.

Somewhere along the line, that seems to have gotten changed, and now,
domain name components can consist entirely of digit sequences.

Can anyone help me out and tell me which RFC, specifically, amended
RFC 1035 so as to allow this?