 It would be premature, however, to deny Ludwig any influence on the development of quantum theory. There are some achievements, like the generalization of observables to POV measures, see Busch et al (2016), which are well known, e.g., in the community practicing quantum information theory, and which finally go back to Ludwig. Usually, the standard reference for these generalizations is not Ludwig but his pupil K. Kraus, see Kraus (1983). Finally it should be mentioned that Ludwig’s axiomatics of quantum mechanics has been revived by new mathematical results, see Casinelli and Lahti (2016). 