Blad, Clara C, van Veldhoven, Jacobus P D, Klopman, Corné, Wolfram, Dieter R, Brussee, Johannes, Lane, J Robert, Ijzerman, Adriaan P, "Novel 3, 6, 7-substituted pyrazolopyrimidines as positive allosteric modulators for the hydroxycarboxylic acid receptor 2 (GPR109A)", Journal of Medicinal Chemistry, 2012