@article{AIHPA_1970__12_3_215_0,
     author = {Mielnik, Bogdan and Pleba\'nski, Jerzy},
     title = {Combinatorial approach to {Baker-Campbell-Hausdorff} exponents},
     journal = {Annales de l'institut Henri Poincar\'e. Section A, Physique Th\'eorique},
     pages = {215--254},
     publisher = {Gauthier-Villars},
     volume = {12},
     number = {3},
     year = {1970},
     mrnumber = {273922},
     zbl = {0206.13602},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1970__12_3_215_0/}
}