Flake, Stephan, Wolfgang Müller, Ulrich Pape, and Jürgen Ruf. “Specification and Formal Verification of Temporal Properties of Production Automation Systems.”https://doi.org/10.1007/978-3-540-27863-4_13__In Integration of Software Specification Techniques for Applications in Engineering, edited by Hartmut Ehrig, Werner Damm, Jörg Desel, Martin Große-Rhode, Wolfgang Reif, Eckehard Schnieder, and Engelbert Westkämper, 3147:206–26. Lecture Notes in Computer Science. Berlin, Heidelberg: Springer-Verlag, 2004.https://doi.org/10.1007/978-3-540-27863-4_13 .

Flake, Stephan, and Wolfgang Müller. “An OCL Extension for Real-Time Constraints.”https://doi.org/10.1007/3-540-45669-4_8__In Advances in Object Modelling with the OCL, edited by T. Clark and J. Warmer, 150–71. Berlin, Heidelberg: Springer-Verlag, 2002.https://doi.org/10.1007/3-540-45669-4_8 .