If you have cards that you are using in a report or a paper or class you have to mention where the card information came from. You have to give the source of the information.

To do source cards, you write the bibliographical information for a source on an index card. Number the card. When you find information in the source that you can use, you write it on a separate index card. On this other index card, you put the number of the source card in one corner, and the page number where you found the information in another corner. You can find more information here: http://www.studenthandouts.com/citations...