León Bermúdez, Adan Yovani, and Ramiro Salazar. “Synthesis and Characterization of the Polystyrene - Asphaltene Graft Copolymer by FT-IR Spectroscopy”. CT&F - Ciencia, Tecnología Y Futuro, vol. 3, no. 4, Dec. 2008, pp. 157-6, doi:10.29047/01225383.469.