Bahri, Syamsul, et al. “The Comparison of Hemoglobin Levels, Blood Oxygen Saturation, and Breaths Frequency on The Lowlander and Highlander ”. Jurnal Biologi Tropis, vol. 22, no. 2, Mar. 2022, pp. 353-9, doi:10.29303/jbt.v22i2.3240.