There are several methods you can use in order to combine data from different sources.

1. You can create a stat.definition that contains at least one common key from the different sources. Then you can create a duty collecting data from source 1, then 2 and so on.
2. You can create one stat definition for each source, then you can create a third collecting data from source 1 and 2 based on a SQL against Butlers own database