The SOURCE section resides within the TRACE section within a TrendSpec definition (see Basic TrendSpec Structure).
The SOURCE section has to contain one SOURCE Mandatory Value.
If required, you can specify one or more SOURCE Optional Values after the above mandatory value.
If a TRACE has more than one origin—whereby its value is the sum of two or more sources—the TRACE section has to contain a separate SOURCE section for each origin (see Multiple Source Traces).
Where an ad hoc Trend contains multiple traces, the TrendSpec definition has to include a separate TRACE section and corresponding SOURCE section for each trace (see Multiple Trace Ad Hoc Trends).