Discussion on the paper by Allin and Hand by Smith, PA, Self, A, Michaelson, J, Spence, A, Haskel, J, Murtagh, F, Nason, G, Caan, W, Goldstein, H, King, T, Cocchi, D, Dorling, D, Summa, MG, Le Roux, B, Hall, JF, Herzberg, AM, Liu, H, Longford, NT, Mateu, J, Rondinella, T, Cocchi, D, Ruggeri, K, Stehlik, M, Strelec, L, Vanderweele, TJ, Yu, K, Tian, M, Zini, A, Lara, L, Porcu, E