Plagiarism is happening even in articles submitted to highly influential academic journals. Possible reasons include:
2. Difficult to write in English with English as a second Language.
3. Cultural difference: in Asia, students are taught to memorize and imitate the language and style of past masters in order to become better writers.
4. Increased pressure to publish for researchers.
5. Lack of training and awareness of rules.
You do not need to cite your source if the information is considered as "common knowledge." Common knowledge is any information that the average, educated reader would accept as reliable without having to look it up. However, there is no clear boundary on what is considered as common knowledge.