The CRYSTAL code, 1976–2020 and beyond, a long story by Dovesi, R, Pascale, F, Civalleri, B, Doll, K, Harrison, NM, Bush, I, D'Arco, P, Noël, Y, Rérat, M, Carbonnière, P, Causà, M, Salustro, S, Lacivita, V, Kirtman, B, Ferrari, AM, Gentile, FS, Baima, J, Ferrero, M, Demichelis, R, De La Pierre, M