Visitor visa - pevious visit 45 years back.

[ceekay]

Hi, I am on L1 visa in US...and wish to bring my mother here on B2 visa( visitor visa)...my mom is 72 yrs old and she came to US before in 1970 when my father was doing Phd here. So she might have come as his dependent on F2 visa.
But now we dont have any details of that visit i.e either passport or vis a details..and dates may be tentatively she knows....
now my question is should we mention about this in the visitor visa that I am going to apply to her now>?? and if so what kind of questions can be expected and if we dont mention is there a way they can find it?
Please advice.

[immihelp]

Mention to the best of your knowledge.