1. Ott V. 1948. Die Sauna, ihre Geschichte - die Grundlagen ihrer Wirkung, ihre Anwendung zur Prophylaxe and Therapie. Basel.
2. On early modes of navigation;Lane Fox;Journal of the Anthropological Institute,1875
3. A Viking settlement at Freswick, Caithness;Curle;Proceedings of the Society of Antiquaries of Scotland,1939
4. The medieval fortress of Mietlica in Poland;Maloney;Archaeology,1982