Zanker, JM Max Planck Institute for Biological Cybernetics, Max Planck Society; Former Department Information Processing in Insects, Max Planck Institute for Biological Cybernetics, Max Planck Society;
https://link.springer.com/content/pdf/10.1007/BF01138495.pdf (Publisher version)
Zanker, J. (1990). Theta motion: A new psychophysical paradigm indicating two levels of visual motion perception. Die Naturwissenschaften, 77(5), 243-246. doi:10.1007/BF01138495.