Mualhajri@uod.edu.sa
Kbelaid@uod.edu.sa
Ljaafar@uod.edu.sa
© 2017 Monerah Al-Hajri, Karim Belaid, Lamia Jaafar Belaid, published by Slovak Academy of Sciences, Mathematical InstituteThis work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.