Michał Gil, Alexandr Gorski, Alexander Starukhin, and Jacek Waluk, Fluorescence studies of porphycene in various cryogenic environments, Low Temp. Phys. 45, (2019) [Fiz. Nizk. Temp. 45, 767-773, (2019)] DOI: https://doi.org/10.1063/1.5103259.