In 1969 the , which registered the Gelderlander, was merged with the  studbook, which registered the Groninger, to form the  or "Royal Warmblood Horse Studbook of the Netherlands".
In 1969, the , which documented the Gelderlander, was united with the  studbook, which recorded the Groninger, to form the  or "Royal Warmblood Horse Studbook of the Netherlands", highlighting a connection between two registries.