Schmitt et al., SEN12MS – A Curated Dataset of Georeferenced Multi-spectral Sentinel-1/2 Imagery for Deep Learning and Data Fusion, ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., IV-2/W7, 153–160, 2019.
You can download the data from https://mediatum.ub.tum.de/1474000