Does anyone have a direct link to the page where it says as a Platinum member you can bring a child as well as one guest into the lounge, if flying with a SkyTeam airline?

Last experience was on 19th July, flying SGN-SIN on VN. We were refused access outright at the lounge, even if I didn't have companions, because we were in Economy class. This sort of thing really doesn't bother me, because I see the whole access thing as a bit of a lottery anyway (away from AFKL I never assume I can automatically get admitted). And there really wasn't much time left before boarding anyway.
Just to add to that, I was refused Sky Priority at SGN as well, being told it was for Business class only. (SGN is Ho Chi Minh City, Vietnam, by the way).