If you use PynPoint in your publication then please cite Stolker et al. (2019). Please also cite Amara & Quanz (2012) as the origin of PynPoint, which focused initially on the use of principal component analysis (PCA) as a PSF subtraction method. In case you use specifically the PCA-based background subtraction module or the wavelet based speckle suppression module, please give credit to Hunziker et al. (2018) or Bonse et al. (preprint), respectively.