Consider the following relation: Articles (ID, title, journal, issue, year, startpage, endpage. TR-ID) It contains information on articles published in scientific journals. Each article has a unique ID, a title information on where to find it (name of journal what issue, and on which pages). Also, if results/ideas of an article previously appeared in a "technical report" (TR) the TR-ID of this technical report can be specified. Finally, we know that for each journal, an issue with a given number is punished in a single year. The following is an instance of the relation: Consider the following relation: Articles (ID, title, journal, issue, year, startpage, endpage. TR-ID) It contains information on articles published in scientific journals. Each article has a unique ID, a title information on where to find it (name of journal what issue, and on which pages). Also, if results/ideas of an article previously appeared in a "technical report" (TR) the TR-ID of this technical report can be specified. Finally, we know that for each journal, an issue with a given number is punished in a single year. The following is an instance of the relation