O. P. Frota, A. M. Ferreira, L. da S. Barcelos, E. Watanabe, N. C. P. Carvalho, and M. A. Rigotti, “ Collection of tracheal aspirate: safety and microbiological concordance between two techniques ”, Rev. Esc. Enferm. USP, vol. 48, no. 4, pp. 618–624, Aug. 2014, doi: 10.1590/S0080-623420140000400007.