Yes, that's exactly what I wrote. He made a book about Bulgaria.
Sven is a Swedish name, the Norwegian form is Svein. Gjestvang was born in Norway and Even is a fairly common name in there.
I don't know much about cyrillic, but I have always thought that S looked like a C in cyrillic.
So Sven would be something like Свен?
It is a very nice group of documents to a quite important person. Unfortunately there are three documents missing which the seller didn't have. They only had seven of the documents and as far as I know Gjestvang received ten medals/orders.