Cooperation-based Invariants for OO Languages. - Ronald Middelkoop; Cornelis Huizing; Ruurd Kuiper 001; Erik J. Luit (FACS, 2005)

Invariants for Non-Hierarchical Object Structures. - Ronald Middelkoop; Cornelis Huizing; Ruurd Kuiper 001; Erik J. Luit (SBMF, 2006)

Specification and Verification of Invariants by Exploiting Layers in OO Designs. - Ronald Middelkoop; Cornelis Huizing; Ruurd Kuiper 001; Erik J. Luit (Fundam. Informaticae, 2008)

Proving Consistency of Pure Methods and Model Fields. - K. Rustan M. Leino; Ronald Middelkoop (FASE, 2009)

Pandora's Box. - Ronald Middelkoop; Cornelis Huizing; Ruurd Kuiper 001; Erik J. Luit (HOWARD-60, 2014)