A 66-page PDF description of the professional system that grew out of the Italian system created for the Dutch junior team but is now distinctly Dutch, exciting to play, used by pairs such as Brink-Drijver and de Leon-Sprinkhuizen.
Professional Dutch Doubleton Bidding System
A complete description of the system played by Brink-Drijver, de Leon-Sprinkhuizen, and several other top Dutch partnerships. The system has won several World or European championships, and in Covid, online events.
The system originally comes from one designed by Benito Garozzo for the Dutch junior team, but the Dutch junior style is to preempt a lot. And open kamikaze notrump when possible. It is now a completely distinct Dutch system, lots of takeout doubles, and an interesting approach to slam bidding, where the default is quantitative with a major fit (cue-bidding is the exception), but lots of cue-bidding and Last Train for the minor suits.
Plus, it is similar in general framework to Standard American (quickly diverging) so can be played in most ACBL events, and you can pick and choose which features you want to add to your system.
With all the structurally interesting features, in practice the preempts and other jumps are most common. Get your competitive bidding agreements down solid if you want to play against it.
The file is a 66-page PDF of the bidding tree.