Some researchers purchase various printed forms from genealogical societies or genealogical vendors; others generate their own by computer. Two popular forms for keeping track of copied information are the research log and the correspondence log. The research log, also called a calendar, is a running list of sources checked; annotations can indicate whether a particular source revealed anything. The log shows all sources checked and acts as a table of contents to the research notes. The correspondence log lists all the letters you send and receive, perhaps with a number key written on the letters so they can be stored and easily retrieved. The correspondence log tells you if you did or did not reply to your aunt or if it has really been six months since you sent to New York City for a birth certificate. Some family historians prefer to keep track of all research activity, including correspondence, in a single research log.