References

Professor Ken Walters, Department of Mathematics, University of Wales, Aberystwyth, Dyfed SY23 3BZ, UK.
E-mail: kew@aber.ac.uk

Professor Ahmad Alawaneh, Department of Mathematics, Al al-Biat University, (On leave from Jordan University).
E-mail: aalawneh@aabu.edu.jo

Professor Samir Hadid, Department of Mathematics, Ajman Scientific University, Ajman, UAE. 
E-mail: sbhadid@yahoo.com

Professor Muhammad Aslam Noor, Department of Mathematics, COMSATS Institute of Information Technology, Islmabad, Pakistan.
E-mail: noormaslam@hotmail.com

Professor Abdul-Majid Wazwaz, Department of Mathematics and Computer Science,
    Saint Xavier University, Chicago, IL 60655, USA. E-mail: wazwaz@sxu.edu