X. Song, et al., “PLGA Nanoparticles Simultaneously Loaded with Vincristine Sulfate and Verapamil Hydrochloride: Systematic Study of Particle Size and Drug Entrapment Efficiency,” International Journal of Pharmaceutics, Vol. 350, No. 1-2, 2008, pp. 320-329.
doi:10.1016/j.ijpharm.2007.08.034