1. American Public Health Association (APHA). (1998). In L. S. Clesceri, A. E. Greenberg, & A. D. Eaton (Eds.), Standard methods for the examination of water and wastewater (20th ed.). Washington: APHA.
2. Brusick, D. J., & Young, R. R. (1981). IERL-RTP procedures manual: Level 1 environmental assessment biological test. EPA-600/8-81-024. Washington: U.S. Environmental Protection Agency.
3. Constantin, M. J., & Owens, E. T. (1982). Introduction and perspectives of plant genetic and cytogenetic assays. A report of the U.S. Environmental Protection Agency Gene-Tox Programme. Mutation Research, 99, 1–12.
4. Dutka, B. J. (1996). Bioassays-summary of the 18 years work, NWRI, Canada Water Tox Workshop, Theme Paper, IDRC, Canada.
5. Fatima, R. A., & Ahmad, M. (2005). Certain antioxidant enzymes of Allium cepa as biomarkers for the detection of toxic heavy metals in wastewater. Science of the Total Environment, 346, 256–273.