Source: https://www.researchgate.net/profile/Rodrigo_Torres-Castro/publication/282573763_Effects_of_air_stacking_versus_glossopharyngeal_breathing_on_maximum_insufflation_capacity_in_children_and_adolescents_with_neuromuscular_disease/links/561278bf08ae83674f4347dd/Effects-of-air-stacking-versus-glossopharyngeal-breathing-on-maximum-insufflation-capacity-in-children-and-adolescents-with-neuromuscular-disease.pdf