1. Institute of Astronomy and National Astronomical Observatory Bulgarian Academy of Sciences Sofia Bulgaria
2. Department of Physics and Astronomy Shumen University “Episkop Konstantin Preslavski” Shumen Bulgaria
3. Hamburger Sternwarte Universität Hamburg Hamburg Germany
4. Astrophysics Research Institute Liverpool John Moores University Liverpool UK
5. Office of the Vice Chancellor Botswana International University of Science and Technology Palapye Botswana