@misc{cryptoeprint:1996:013,
    author = {Carlo Blundo, Alfredo De Santis, and Douglas R. Stinson},
    title = {On the Contrast in Visual Cryptography Schemes},
    howpublished = {Cryptology ePrint Archive, Report 1996/013},
    year = {1996},
    url = {http://eprint.iacr.org/1996/013},
}