Tunggal Setiawan, T. 2016. STROKE RATE (SR) AND STROKE LENGTH (SL) FREESTYLE SWIMMER INDONESIAN STUDENT PARTICIPANTS POPNAS 2009. Jorpres (Jurnal Olahraga Prestasi). 8, 2 (Aug. 2016), 36–48. DOI:https://doi.org/10.21831/jorpres.v8i2.10292.