Attribute: Source

When used in the <Identifer> element, it indicates the type of unique identifier associated with a contributor. When used in the <OtherID> element, it identifies the source of the additional identifier associated with the record.

In <OtherID>

Source (NASA|KIE|PIP|POP|ARPL|CPC|IND|CPFH|CLML|NRCBL|NLM|QCIM) #REQUIRED

In <Identifier>

Source CDATA #REQUIRED