Partov, Doncho N.; Christo T. Christov; Vesselin K. Kantchev; Dobromir E. Dinev; Aleksander K. Taushanov; Edelvais E. Popova; Deian P. Mitev. "State of Art of Historic Structures in Bulgaria"(PDF). ARCCHIP Advanced Research Centre for Cultural Heritage Interdisciplinary Projects. pp. 3–4. Archived from the original(PDF) on 18 July 2011. Retrieved 30 May 2011.
Partov, Doncho N.; Christo T. Christov; Vesselin K. Kantchev; Dobromir E. Dinev; Aleksander K. Taushanov; Edelvais E. Popova; Deian P. Mitev. "State of Art of Historic Structures in Bulgaria"(PDF). ARCCHIP Advanced Research Centre for Cultural Heritage Interdisciplinary Projects. pp. 3–4. Archived from the original(PDF) on 18 July 2011. Retrieved 30 May 2011.