What elements/types in GML are used in ISO 19139?

I did a survey.

= simple references
== reference to attributegroup in GML
ref gml:AggregationAttributeGroup

== reference to elements in GML
ref gml:AbstractCoordinateOperation
ref gml:AbstractCoordinateSystem
ref gml:AbstractCRS
ref gml:AbstractDatum
ref gml:AbstractGeneralOperationParameter
ref gml:AbstractGeometry
ref gml:AbstractTimePrimitive
ref gml:BaseUnit
ref gml:ConventionalUnit
ref gml:CoordinateSystemAxis
ref gml:DerivedUnit
ref gml:Ellipsoid
ref gml:OperationMethod
ref gml:Point
ref gml:pos
ref gml:PrimeMeridian
ref gml:UnitDefinition

= type reference
== attributes using GML type
type gml:NilReasonType

== elements using GML type
type gml:AngleType
type gml:CodeType
type gml:LengthType
type gml:MeasureType
type gml:ScaleType

== types extending GML's one
base gml:AbstractCoordinateOperationType
base gml:AbstractCRSType
base gml:AbstractDatumType
base gml:AffineCSType
base gml:BaseUnitType
base gml:CartesianCSType
base gml:CompoundCRSType
base gml:ConcatenatedOperationType
base gml:ConventionalUnitType
base gml:ConversionType
base gml:CoordinateSystemAxisType
base gml:CylindricalCSType
base gml:DefinitionType
base gml:DerivedCRSType
base gml:DerivedUnitType
base gml:DictionaryType
base gml:EllipsoidalCSType
base gml:EllipsoidType
base gml:EngineeringCRSType
base gml:EngineeringDatumType
base gml:GeocentricCRSType
base gml:GeodeticCRSType
base gml:GeodeticDatumType
base gml:GeographicCRSType
base gml:IdentifiedObjectType
base gml:ImageCRSType
base gml:ImageDatumType
base gml:LinearCSType
base gml:OperationMethodType
base gml:OperationParameterGroupType
base gml:OperationParameterType
base gml:PassThroughOperationType
base gml:PolarCSType
base gml:PrimeMeridianType
base gml:ProjectedCRSType
base gml:SphericalCSType
base gml:TemporalCRSType
base gml:TemporalDatumType
base gml:TimeCSType
base gml:TransformationType
base gml:UnitDefinitionType
base gml:UserDefinedCSType
base gml:VerticalCRSType
base gml:VerticalCSType
base gml:VerticalDatumType

== elements of types that extend GML's type
substitutionGroup gml:AffineCS
substitutionGroup gml:BaseUnit
substitutionGroup gml:CartesianCS
substitutionGroup gml:CompoundCRS
substitutionGroup gml:ConcatenatedOperation
substitutionGroup gml:ConventionalUnit
substitutionGroup gml:Conversion
substitutionGroup gml:CoordinateSystemAxis
substitutionGroup gml:CylindricalCS
substitutionGroup gml:Definition
substitutionGroup gml:DerivedCRS
substitutionGroup gml:DerivedUnit
substitutionGroup gml:Dictionary
substitutionGroup gml:Ellipsoid
substitutionGroup gml:EllipsoidalCS
substitutionGroup gml:EngineeringCRS
substitutionGroup gml:EngineeringDatum
substitutionGroup gml:GeocentricCRS
substitutionGroup gml:GeodeticCRS
substitutionGroup gml:GeodeticDatum
substitutionGroup gml:GeographicCRS
substitutionGroup gml:ImageCRS
substitutionGroup gml:ImageDatum
substitutionGroup gml:LinearCS
substitutionGroup gml:OperationMethod
substitutionGroup gml:OperationParameter
substitutionGroup gml:OperationParameterGroup
substitutionGroup gml:PassThroughOperation
substitutionGroup gml:PolarCS
substitutionGroup gml:PrimeMeridian
substitutionGroup gml:ProjectedCRS
substitutionGroup gml:SphericalCS
substitutionGroup gml:TemporalCRS
substitutionGroup gml:TemporalDatum
substitutionGroup gml:TimeCS
substitutionGroup gml:Transformation
substitutionGroup gml:UnitDefinition
substitutionGroup gml:UserDefinedCS
substitutionGroup gml:VerticalCRS
substitutionGroup gml:VerticalCS
substitutionGroup gml:VerticalDatum