> С начала XII века на месте современных Холмогор располагался дальний новгородский «Ивани-Погост», впервые упомянутый в уставной грамоте Новгородского князя Святослава Ольговича 1138 года о поступлении дани с заволоческих владений.
Thank you! It could be true, but frankly I wouldn't trust ru.wikipedia too blindly, especially when it comes to small towns history, because there are lots of local lore gatherers with original researches, and nobody cares to verify their contributions. I can't check the mentioned act of Sviatoslav now, that would require to search for a real paper book :) But I'm quite sure it should be 1137, not 1138 for starters.