Several Changes - Several Clinical
Several Clinical Factors - Several Concentrations
Several Concerns - Several Covariates
Several Criteria - Several Decades
Several Degrees - Several Different Species
Several Different Types - Several Domains

Several Doses - Several Environments
Several Enzymes - Several Factors
Several Families - Several Functions
Several Fungi - Several Haplotypes
Several Hours - Several Important Aspects
Several Important Issues - Several Initiatives
Several Instances - Several Iterations

Several Key Aspects - Several Ligands
Several Limitations - Several Materials
Several Means - Several Methods