Kuhn, Richard Max Planck Institute for Medical Research, Max Planck Society;
http://onlinelibrary.wiley.com/doi/10.1002/cber.19520850603/epdf (Any fulltext)
https://dx.doi.org/10.1002/cber.19520850603 (Any fulltext)
Kuhn, R., & Kainer, H. (1952). Pentaphenyl-Penthaphenyl-Pyrroliumperchlorat. Chemische Berichte, 85(6), 498-507. doi:10.1002/cber.19520850603.