^Beqollari D, Kammermeier PJ. The mGlu(4) receptor allosteric modulator N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide acts as a direct agonist at mGlu(6) receptors. European Journal of Pharmacology. July 2008, 589 (1–3): 49–52. PMID 18593581. doi:10.1016/j.ejphar.2008.06.054.
^Stachowicz K, Kłak K, Kłodzińska A, Chojnacka-Wojcik E, Pilc A. Anxiolytic-like effects of PHCCC, an allosteric modulator of mGlu4 receptors, in rats. European Journal of Pharmacology. September 2004, 498 (1–3): 153–6. PMID 15363989. doi:10.1016/j.ejphar.2004.07.001.