Source of the files:

so.obo: https://github.com/The-Sequence-Ontology/SO-Ontologies/blob/master/so-xp-simple.obo
so-xp.obo: https://github.com/The-Sequence-Ontology/SO-Ontologies/blob/master/so-xp.obo
sofa.obo: https://github.com/The-Sequence-Ontology/SO-Ontologies/blob/master/subsets/SOFA.obo

Current HEAD is 3a1b6bd850cff63ffac60ff3452dc01d319c793c
