@INPROCEEDINGS{morphBM,
    author = {Susskind, J. and Memisevic, R. and Hinton, G. and Pollefeys, M.},
    title = {Modeling the joint density of two images under a Variety of Transformations},
    booktitle = {Proceedings of IEEE Conference on Computer Vision and Pattern Recognition},
    year = {2011}
}