The title of the paper should be writing with capital letters. The author's name has to apply in the middle of the line, near the title. References should be mentioned in the text by a number in square brackets and should be listed alphabetically. Current address followed by e-mail address should apply at the end of the paper, after the references. The paper should have at the beginning an abstract, followed by the keywords. All manuscripts are subject to anonymous review by three independent reviewers. Every letter will be answered. Each author will receive a free copy of the journal.