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 im 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?