1. Postdoctoral Fellow, Dept. of Applied Mathematics, Univ. of Twente, 7522 NB, Enschede, Netherlands; Head of Laboratory, LabMath-Indonesia, Jl. Dago Giri No. 99, Bandung 40391, Indonesia (corresponding author).,
2. Researcher, LabMath-Indonesia, Jl. Dago Giri No 99, Bandung, 40391, Indonesia,
3. Professor, Dept. of Applied Mathematics, Univ. of Twente, 7522 NB, Enschede, Netherlands; Researcher, LabMath-Indonesia, Jl. Dago Giri No. 99, Bandung 40391, Indonesia.