Sources:
PAC, 1981, 53, 753. 'Symbolism and Terminology in Chemical Kinetics' on page 762 (https://doi.org/10.1351/pac198153030753)
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2265 (https://doi.org/10.1351/pac199668122223)