observational estimates
observational evidence
observational findings
observational follow-up study
observational measures
observational method
observational period
observational results
observational scale

observational studies
observational study
observational study design
observational survey
observational tool
observational uncertainties
observations
observations showing
observations support
observed

observed activity
observed adverse effect level
observed alterations
observed associations
observed behavior
observed behaviour
observed cases
observed changes
observed characteristics
observed compositional variation

observed concentrations
observed correlations
observed data
observed deaths
observed decline
observed decrease
observed defects
observed dependence
observed differences
observed disparities

observed distribution
observed divergence
observed effect
observed X-ray emission