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. p. 4. Archived from the original(PDF) on 18 July 2011. Retrieved 25 November 2010.
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. p. 4. Archived from the original(PDF) on 18 July 2011. Retrieved 25 November 2010.