I have read the Wikipedia rules a few times and As far as I can find it says All reliable sources are by definition both published and accessible to at least some people Sources that are not published e g something someone said to you personally or not accessible e g the only remaining copy of the book is locked in a vault with no one allowed to read it are never acceptable as sources on Wikipedia In my interpretation I can refer to 2000 Jahre Handel und Kultur i m Ostseegebiet Gotland Perle der Ostsee ISBN91 972306 6 9 As far as I can see this book qualifies If you accept this we can go further If you search ISBN91 972306 6 9 on Google you will get 109 results OpenFuture does not accept this Are you reading the rules in the same way