Revisiting canonical quantization of radiation: the role of the vacuum fieldA. M. Cetto, L. de la Peña and J. F. Pérez-BarragánEur. Phys. J. Spec. Top., 232 20-22 (2023) 3339-3344DOI: https://doi.org/10.1140/epjs/s11734-023-00984-5