Bourchier, James. Bulgaria/Language // Encyclopædia Britannica. 11. Т. IV. Cambridge University Press., 1911. с. 786. via Internet Archive: "With the exception of Zlatarski's and Boncheff's geological treatises and contributions by Georgieff, Petkoff, Tosheff and Urumoff to Velnovski's Flora Bulgarica, no original works on natural science have as yet been produced; a like dearth is apparent in the fields of philosophy, criticism and fine art, but it must be remembered that the literature is still in its infancy."
Bourchier, James. Bulgaria/Language // Encyclopædia Britannica. 11. Т. IV. Cambridge University Press., 1911. с. 786. via Internet Archive: "With the exception of Zlatarski's and Boncheff's geological treatises and contributions by Georgieff, Petkoff, Tosheff and Urumoff to Velnovski's Flora Bulgarica, no original works on natural science have as yet been produced; a like dearth is apparent in the fields of philosophy, criticism and fine art, but it must be remembered that the literature is still in its infancy."
