Clue 1: Currency
Currency is important because information can quickly become obsolete. Supporting your thesis statement with facts that have been superseded by new research or recent events weakens your argument. An article about the use of stem cells in scientific research from 1998 would not provide the most accurate information about the status of stem cell research today. Of course, not all assignments require the most current information; older materials can provide an historical or comprehensive understanding of your topic.
How do you know if the timeliness of your information is appropriate?