Introduction - If you have any usage issues, please Google them yourself
(1) ICCV1999 Object Recognition from Local Scale-Invariant Features.pdf proposed (2) IJCV2004 Distinctive image features from scale invariant keypoints.pdf summary (3) CVPR2004 PCA-SIFT: A More Distinctive Representation for Local Image Descriptors.pdf plus PCA down Victoria
CVPR2004 PCA-SIFT:A More Distinctive Representation for Local Image Descriptors.pdf
ICCV1999 Object Recognition from Local Scale-Invariant Features.pdf
IJCV2004 Distinctive image features from scale invariant keypoints.pdf