M. Blondel, A. Fujino, N. Ueda, “Convex Factorization Machines,” in Proc. European Conference on Machine Learning and Principles and Practice
of Knowledge Discovery in Databases, 2015.  M. Blondel, V. Niculae, T. Otsuka, N. Ueda, “Multi-output Polynomial Networks and Factorization Machines,” in Proc. Neural Information
Processing Systems, 2017.