. 2021 May 11;60(Suppl 1):e32–e43. doi: 10.1055/s-0041-1728757
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This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License, which permits unrestricted reproduction and distribution, for non-commercial purposes only; and use and reproduction, but not distribution, of adapted material for non-commercial purposes only, provided the original work is properly cited.
Fig. 4.
Stacked model.