1ADIYAMAN UNIVERSITY, FACULTY OF ARTS AND SCIENCES, DEPARTMENT OF MATHEMAT- Ics, 02040 ADIYAMAN, TURKEY
2CUMHURIYET UNIVERSITY, FACULTY OF ARTS AND SCIENCES, DEPARTMENT OF MATHE- MATICS, 58140 Sivas, TURKEY
3ADIYAMAN UNIVERSITY, FACULTY OF ARTS AND SCIENCES, DEPARTMENT OF MATHEMAT- ICs, 02040 ADIYAMAN, TURKEY