Cordelia Schmid Andrew Zisserman Roger Mohr Integrating Geometric and Photometric Information for Image Retrieval. 217-233 1999 conf/shape/1999 Shape, Contour and Grouping in Computer Vision http://link.springer.de/link/service/series/0558/bibs/1681/16810217.htm db/conf/shape/shape1999.html#SchmidZM99