Astrika, G., A. Panggayuh, and T. Mardiyanti. “The Effect Of Birthing Ball On The Duration Of Active Phase In Primigravida At Pmb Yulis Indriana, Malang”. Jurnal Pendidikan Kesehatan (e-Journal), vol. 8, no. 2, Oct. 2019, pp. 164-75, doi:10.31290/jpk.v8i2.1021.