Irish et al. (1995)

Irish L. B., Lesso W. G., Barret M. E., Malina J. F., Charbeneau R. J. & Ward G. H. 1995. An Evaluation of the Factors Affecting the Quality of Highway Runoff in the Austin, Texas Area, Technical Report CRWR 264. Center for Research in Water Resources.
Data from Yousef Y. A., Wanielista M. P. & Harper H. H. (1986) Removal of Highway Contaminants by Roadside Swales Washington DC: NRC TRB Transportation Research Record 1017, 1986.