1. 1. Stoyanov, S., I. Popchev. Evolutionary Development of an Infrastructure Supporting the Transition from CBT to e-Learning. – Cybernetics and Information Technologies, Vol. 6, 2006, No 2, pp. 101-114.
2. 2. Stoyanov, S., I. Popchev, E. Doychev, D. Mitev, V. Valkanov, A. Stoyanova-Doycheva, V. Valkanova, I. Minov. DeLC Educational Portal. – Cybernetics and Information Technologies, Vol. 10, 2010, No 3, pp. 49-69.
3. 3. Sandalski, M., A. Stoyanova-Doycheva, I. Popchev, S. Stoyanov. Development of a Refactoring Learning Environment. – Cybernetics and Information Technologies, Vol. 11, 2011, No 2, pp. 46-64.
4. 4. Stancheva, N., A. Stoyanova-Doycheva, S. Stoyanov, I. Popchev, V. Ivanova. A Model for Generation of Test Questions. – Compt. Rend. Acad. bulg. Sci., Vol. 70, 2017, No 5, pp. 619-630.
5. 5. Stancheva, N., A. Stoyanova-Doycheva, S. Stoyanov, I. Popchev, V. Ivanova. An Environment for Automatic Test Generation. – Cyberbetics and Information Technologies, Vol. 17, 2017, No 2, pp. 183-196.