Authors
Dragomir Marchev
University of Shumen, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Kiril Stoyanov
Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
Vladislav Marchev
University of Shumen, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
Radoslav Zamanov
Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Sofia, Bulgaria
Borislav Borisov
University of Shumen, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Doroteq Vasileva
University of Shumen, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Teodora Atanasova
University of Shumen, Faculty of Natural Sciences, Department of Physics and Astronomy, Shumen, Bulgaria
Nataliya Pavlova
University of Shumen, Faculty of Mathematics and Informatics, Department of Algebra and Geometry, Shumen, Bulgaria