@article{202103.0737,
	doi = {},
	url = {https://doi.org/},
	year = 2021,
	month = {March},
	publisher = {Preprints},
	author = {Alberto Franceschini},
	title = {Photon-photon Interactions and the Opacity of the Universe in Gamma-Rays},
	journal = {Preprints}
}