Source: http://yann.lecun.com/exdb/mnist/

1. Title: THE MNIST DATABASE of handwritten digits

2. Sources:
   -- Yann LeCun, Courant Institute, NYU
   -- Corinna Cortes, Google Labs, New York
   -- Christopher J.C. Burges, Microsoft Research, Redmond

3. Relevant Information:

    The MNIST database of handwritten digits, available from this page,
    has a training set of 60,000 examples, and a test set of 10,000 examples.
    It is a subset of a larger set available from NIST. The digits have been
    size-normalized and centered in a fixed-size image.

    It is a good database for people who want to try learning techniques and
    pattern recognition methods on real-world data while spending minimal
    efforts on preprocessing and formatting.

    Four files are available on this site:

    train-images-idx3-ubyte:  60,000 training set images
    train-labels-idx1-ubyte:  60,000 training set labels
    t10k-images-idx3-ubyte:   10,000 test set images
    t10k-labels-idx1-ubyte:   10,000 test set labels