Published in 1998 There are ... items referenced. 1998 -- A.J. van der Schaft Implicit Hamiltonian systems with symmetry 1998 -- Stefano Stramigioli, Bernhard Maschke, Arjan van der Schaft Passive Output Feedback and Port Interconnection 1998 -- Morten Dalsmo, Arjan van der Schaft On Representations and Integrability of Mathematical Structures in Energy-Conserving Physical Systems