{"id":"000773691","type":"book","title":"Kreposti i ukrepitelni sǎorǎženija v krǎnskata srednovekovna oblast","publisher":"Izd. na Bǎlgarskata akad. na naukite","publisher-place":"Sofija","author":[{"family":"Popov","given":"Atanas."}],"issued":{"raw":"1982"}}