Zinc potassium phosphate hexahydrate crystals for nonlinear optics V. Krishnakumar, S. Manohar, R. Nagalakshmi, M. Piasecki, I. V. Kityk and P. Bragiel Eur. Phys. J. Appl. Phys., 47 3 (2009) 30701 Published online: 12 June 2009 DOI: 10.1051/epjap/2009094