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