1. UNWTO (2020). Retrieved from https://www.unwto.org/.
2. Pindyck, R. S. and Rubinfeld, D. I. (2018). Microeconomics. Global Edition (9 ed.). Harlow, United Kingdom: Pearson Education Limited.
3. Ivanchuk, O. V., & Liuta, O. V. (2019). Theoretical approaches to determining the essence of the "Profit" category. Problemy ta perspektyvy rozvytku finansovo-kredytnoi systemy Ukrainy: proceedings of all-Ukrainian Scientific and Practical online Conference. Sumy: Sumskyi derzhavnyi universytet, 37-40. (in Ukrainian)
4. Hultaichuk, V. V. (2014). Historical prerequisites for the emergence and development of the concept of "profit". Innovatsiinyi rozvytok ta konkurentospromozhnist pidpryiemstv i sektoriv ekonomiky : proceedings of all-Ukrainian Scientific and Practical online Conference graduate students, young scientists and students dedicated to Science Day. Zhytomyr: ZhDTU, 29-30. (in Ukrainian)
5. Hudzenko, N. M. (2014). Evolution of the concept of "income" in economic science. Visnyk ONU imeni I.I. Mechnikova, 19(5-6), 125-129. (in Ukrainian)