Leta, V. V. (2024). Statistical analysis of water quality indicators in the Tisa River’s transboundary section. Actual Issues of Modern Science. European Scientific e-Journal, 33, 96–107.

Veselinova, N. (2022). Die Natur als Faktor bei der geographischen Erklärung der bulgarischen historischen Geographie (=Nature as a factor in the geographical explanation of Bulgarian historical geography). Actual Issues of Modern Science. European Scientific e-Journal, 23, 24−32. (In Ger.)

Vladev, D. (2022). Geomorphological characteristic of the plateaus in Northeastern Bulgaria. Actual Issues of Modern Science. European Scientific e-Journal, 22, 63−83.