Petukhova, V. “Theoretical Basis of the Customs Union As a Perfect Form of Free Trade Area Within Intercountry Cooperation Research”. The Journal of V. N. Karazin Kharkiv National University. Series: International Relations. Economics. Country Studies. Tourism, no. 5, 1, pp. 54-57, https://periodicals.karazin.ua/irtb/article/view/6614.