cite those sources. then say that three times fast.

i regret that i did not manage to add sources to my tree as i was building the first few branches. now some of those sources are gone and i cannot find them to add to my tree now. dont hesitate to add those important web links to the facts page for later referral or just so no one will say "hey look at that. no sources." 

a quote or copy of that source would be a good idea as well as some sites disappear after you find them, like mundia.com which was a free to use ancestry site but now is gone.