Vanderhaegen, Bart, and Guy Derdelinckx. “Characterization of Flavour Compounds in Fresh and Aged Beer by Purge and Trap-Gas Chromato-Graphy-Mass Spectrometry”. BrewingScience, vol. 59, no. 11/12, Dec. 2005, pp. 1-9, https://brewingscience.de/index.php/brewingscience/article/view/526.