Martyshenko, N. S., E. B. Kmet, and A. G. Kim. “The Study of the Cycle of Packaged Tours from the Primorsky Territory”. International Journal of Economics and Financial Issues, vol. 5, no. 3S, Dec. 2015, pp. 257-62, https://www.econjournals.com/index.php/ijefi/article/view/1721.