http://eprints.umm.ac.id/65708/3/BAB%202.pdf
http://eprints.umm.ac.id/43334/3/jiptummpp-gdl-erinaebhip-50409-3-babii.pdf https://repository.uinjkt.ac.id/dspace/bitstream/123456789/38256/10/BAB%209%20Respirasi.pdf
