Avik, D. “A Note on Invariant Submanifolds of $(k, μ)$-Contact Manifolds”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 11, Nov. 2010, pp. 1555–1560, https://umj.imath.kiev.ua/index.php/umj/article/view/2979.