Ruttkowski E, Labitzke R, Khanh NQ, Löffler F, Gottschalk M, Jany KD (September 1990). "Cloning and DNA sequence analysis of a polygalacturonase cDNA from Aspergillus niger RH5344". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1087 (1): 104–6. doi:10.1016/0167-4781(90)90130-t. PMID2400785.
Ruttkowski E, Labitzke R, Khanh NQ, Löffler F, Gottschalk M, Jany KD (September 1990). "Cloning and DNA sequence analysis of a polygalacturonase cDNA from Aspergillus niger RH5344". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1087 (1): 104–6. doi:10.1016/0167-4781(90)90130-t. PMID2400785.