Valenzuela Toledo, C. A., J. Beltrán Almeida, and J. Motoa-Manzano. “De Sitter Symmetries and Inflationary Scalar-Vector Models”. Universitas Scientiarum, vol. 21, no. 3, Oct. 2016, pp. 219-43, doi:10.11144/Javeriana.SC21-3.dssa.