G. V. Guimarães, V. D' Avila, E. A. Bocchi, and V. O. Carvalho, “ Norepinephrine remains increased in the six-minute walking test after heart transplantation ”, Clinics, vol. 65, no. 6, pp. 587–591, Jan. 2010, doi: 10.1590/S1807-59322010000600005.