Sohrabi, M.R., et al. “Simultaneous Determination of Acetyl Salicylic Acid and Acetaminophen in Acetaminophen-Caffeine-Aspirin (ACA) Tablets by FT-IR ATR Spectrometry With Multivariate Calibration Data Treatment”. Asian Journal of Chemistry, vol. 17, no. 1, Mar. 2016, pp. 541-7, https://asianpubs.org/index.php/ajchem/article/view/19830.