1. Trendafilova, A.M.: Development of an environment for building a common catalogue for representation of the culture-historical heritage of Bulgaria. In: Cybernetics and Information Technologies, vol. 7, Issue 1, Bulgarian Academy of Sciences, pp. 95–105 (2007)
2. http://cco.vrafoundation.org/index.php/aboutindex/who_is_using_cco/
3. Stoyanov, S., Stoyanova-Doycheva, A., Glushkova, T., Doychev, E.: Virtual physical space—an architecture supporting internet of things applications. In: XX-th International Symposium on Electrical Apparatus and Technologies SIELA 2018, 3–6 June 2018, Bourgas, Bulgaria (2018)
4. Stoyanov, S., Orozova, D., Popchev, I.: Internet of things water monitoring for a smart seaside city. In: XX-th International Symposium on Electrical Apparatus and Technologies SIELA 2018, 3–6 June 2018, Bourgas, Bulgaria (2018)
5. Glushkova, T., Miteva, M., Stoyanova-Doycheva, A., Ivanova, V., Stoyanov, S.: Implementation of a personal internet of thing tourist guide. Am. J. Comput. Commun. Control 5(2) (2018). ISSN: 2375-3943, 39-51