@article{GreefrathOldenburgSilleretal.2021,
  author    = {Gilbert Greefrath and Reinhard Oldenburg and Hans-Stefan Siller and Volker Ulm and Hans-Georg Weigand},
  title     = {Basic Mental Models of Integrals - Theoretical Conception, Development of a Test Instrument, and first Results},
  journal   = {ZDM - Mathematics Education},
  volume    = {53},
  doi       = {10.1007/s11858-020-01207-0},
  year      = {2021},
}