Silveira, Ana Paula C., et al. “Comparison Among Positive Pressure, Standard Physioterapy and Incentive Spirometry After Cardiac Surgery: Literature Review”. Medicina (Ribeirao Preto), vol. 44, no. 4, Dec. 2011, pp. 338-46, https://doi.org/10.11606/issn.2176-7262.v44i4p338-346.