org.opengis.referencing.crs
Interfaces 
CompoundCRS
CoordinateReferenceSystem
CRSAuthorityFactory
CRSFactory
DerivedCRS
EngineeringCRS
GeneralDerivedCRS
GeocentricCRS
GeodeticCRS
GeographicCRS
ImageCRS
ProjectedCRS
SingleCRS
TemporalCRS
VerticalCRS