Sources are commonly journals, but they are not restricted to being journals. This table contains data directly pertaining to any and all types of Sources we know that ISI data describes. It has the following fields:

Sources are guaranteed to be unique by the combination of all of their fields, not just their primary keys. So for example, even though Sources used to be merged by their matching "J9" fields, they will now not be matched unless all of their other fields are exactly the same (including empty).

In the various built-in extractions, when Sources are specified in the standard source fields ("J9", "SO", etc.), they are considered to be inner sources. When they are specified as part of reference strings and are not merged, they are considered to be outer sources.