Michael L. Agnew, PhD, is Senior Field Technical Manager for Syngenta Professional Products, Greensboro, North Carolina. He is coauthor of Mathematics of Turfgrass Maintenance, Fourth Edition (Wiley) Nancy H. Agnew, PhD, is Student Programs Instructor at Longwood Gardens, Inc., Kennett Square, Pennsylvania. She teaches a course in horticulture mathematics Nick E. Christians, PhD, is University Professor of Horticulture at Iowa State University, Ames, Iowa. His previous books include Mathematics of Turfgrass Maintenance, Fourth Edition, and Fundamentals of Turgrass Management, Third Edition (Wiley) Ann Marie Vanderzanden, PhD, is Associate Professor of Horticulture at Iowa State University, Ames, Iowa. She is coauthor of Landscape Design: Theory and ApplicationChristians, Nick is the author of 'Mathematics for the Green Industry', published 2008 under ISBN 9780470136720 and ISBN 0470136723.