1] Hristo Hristov STUDY OF THE RHEOLOGICAL PROPERTIES OF SOME ESSENTIAL OILS USED IN COSMETICS AND PHARMACEUTICALS" - Contemporary Materials 2025 - Savremeni Materijali, 11.08.2025.
(https://ekonferencije.com/sr1/rad/study-of-the-rheological-prope/6746)

2] Hristo Hristov STUDY OF THE ENERGY POTENTIAL OF RENEWABLE ENERGY SOURCES IN THE REGION OF GABROVO FOR USE IN HYBRID WIND-PHOTOVOLTAIC STAND-ALONE SYSTEM" - Contemporary Materials 2015 - Savremeni Materijali, 15.07.2015.
(https://ekonferencije.com/sr1/rad/study-of-the-energy-potential-/4053)