No patent, online document, unpublished material, working paper, or preprint is included in the database
1. Peer-reviewed journals
We cover all peer-reviewed scholarly journals. There is a debate about the exclusion of predatory journals from scientific databases. Since there is no bulletproof for identifying them, we decided to cover all scholarly journals without prejudice. Furthermore, the total number of publications by those journals is negligible.
2. Book chapters
We cover book chapters that are similar to scholarly articles in edited volumes.
Books with original contents (as opposed to textbooks and explanatory titles) are also covered, but still, the coverage is not comprehensive.
4. Conference proceedings
Full-length articles in proceedings are covered. It is debatable if conference proceedings should be covered along with journal articles. We decided to cover proceedings since they play critical roles in some disciplines.