Undefined property 'subject' on MedicalGuideline and wikidoc types

 <http://schema.org/MedicalGuideline>MedicalGuideline<http://schema.org/MedicalGuideline>,
MedicalGuidelineRecommendation<http://schema.org/MedicalGuidelineRecommendation>,
MedicalGuidelineContraindication<http://schema.org/MedicalGuidelineContraindication>,
and MedicalScholarlyArticle <http://schema.org/MedicalScholarlyArticle> include
the 'subject' property in their examples, but this property is not
defined anywhere
on schema.org <http://schema.org/docs/full.html>.

Is 'guidelineSubject' the property meant to be used in these examples?

Steph.