Stoyan, Yuri G., Igor Grebennik, Viacheslav Kalashnikov, and Oleksandr Lytvynenko. 2018. “Enumeration and Generation of Permutations With a Partially Fixed Order of Elements”. International Journal of Combinatorial Optimization Problems and Informatics 8 (1), 19-30. https://ijcopi.org/index.php/ojs/article/view/4.