A research article is a regular article which aims to present new findings. 2. Letters to the Editor: A letter to the editor is a short article which aims to present new findings that require fast publication procedures. 3. Notes: A note is an article (regular or short) which aims to present rather new findings. 4. Comments: A comment is a short article that makes comments on another article already published by this journal or replies to a comment; 5. Review Articles: A review article is an article which aims to present comprehensively already existing findings.6. Lecture Notes: A lecture note is a short review article. 7. Monographs: A monograph is a thesis of one or more authors on a unique subject; apart from the standard reviewing procedures, a monograph must also be accepted from a committee of specialists appointed by the Editor. 8. Innovations: An innovation is an article which aims to present new procedures or devices. 9. Selected conference articles: Upon an agreement with a conference committee, selected papers may be published by the Journal in a special section. In this case the editor will appoint in collaboration with the conference committee guest editors.