Arimbi, A., P. Patmawati, S. Silatulrahmi, and N. Nurliani. “Fartlek Training on the Improvement of Hemoglobin Conditions and Hematocrit”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 38, no. 2, May 2018, pp. 42-46, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/8836.