R. G. Garrett G. Closs K.J. Ellefsen J.E. Kilburn J.D. Horton S. M. Smith C.C. Johnson A. Demetriades J. Locutura R. T. Ottesen D. B. Smith 2011 application/pdf en John Wiley & Sons, Ltd. Geochemical mapping of the Denver, Colorado (USA) urban area: A comparison of studies in 1972 and 2005 chapter