http://hl7.org/fhir/StructureDefinition/observation-precondition|4.0.1

Other preceding or concurrent observations that must be known to correctly interpret the the observation. For example an fiO2 measure taken alongside of a SpO2 measurement. See the [Observation notes](observation.html#notes) section for additional guidance.
NameFlagsCardTypeDescription & Constraints
Extension
0..*Other Observations needed to aid in the interpretation of the source observation.
 
extension
?..0
 
url
?..?
 
value[x] *
1..?
 
 
valueReference *
1..?Reference