f:Observation/f:subject id: maximum cardinality of 'id' is 1 reference: maximum cardinality of 'reference' is 1 type: maximum cardinality of 'type' is 1 identifier: maximum cardinality of 'identifier' is 1 display: maximum cardinality of 'display' is 1 f:Observation/f:referenceRange modifierExtension: minimum cardinality of 'modifierExtension' is 1 modifierExtension: maximum cardinality of 'modifierExtension' is 1 text: minimum cardinality of 'text' is 1