S. Elaydi, Trinity University, San Antonio, Texas, USA. G. Ladas, University of Rhode Island, Kingston, USA. J. Popendat and J. Rakowski, Poznan University of Technology, Poland.
S. Elaydi, Trinity University, San Antonio, Texas, USA. G. Ladas, University of Rhode Island, Kingston, USA. J. Popendat and J. Rakowski, Poznan University of Technology, Poland.