^pof;
Mathematics,;
University;
of;
Malakand,;
Chakdara;
Dir(Lower),;
Khyber;
Puhtoonkhwa,;
Pakistan;
^pof;
Mathematics;
COMSATS;
IIT;
H-8/1,;
lslamabad;
Pakistan;
^pof;
Mathematics,;
Pusan;
National;
University,;
Busan;
609-735,;
South;
Korea;