Devi Nurtiyasari (Department of Mathematic, Faculty of Mathematics and Natural Science, Universitas Gadjah Mada, Indonesia)
Abdurakhman Abdurakhman (Department of Mathematic, Faculty of Mathematics and Natural Science, Universitas Gadjah Mada, Indonesia)
Muhamad Rashif Hilmi (Department of Mathematic, Faculty of Mathematics and Natural Science, Universitas Gadjah Mada, Indonesia)