xorshift is a derivative work originating from:
http://xoroshiro.di.unimi.it/

- splitmix64 (http://xoroshiro.di.unimi.it/splitmix64.c) 
"""
  Written in 2015 by Sebastiano Vigna (vigna@acm.org)

  To the extent possible under law, the author has dedicated all copyright
  and related and neighboring rights to this software to the public domain
  worldwide. This software is distributed without any warranty.

  See <http://creativecommons.org/publicdomain/zero/1.0/>. 
"""

- xoroshiro128+ (http://xoroshiro.di.unimi.it/xoroshiro128plus.c)
"""
  Written in 2016 by David Blackman and Sebastiano Vigna (vigna@acm.org)
  
  To the extent possible under law, the author has dedicated all copyright
  and related and neighboring rights to this software to the public domain
  worldwide. This software is distributed without any warranty.
  
  See <http://creativecommons.org/publicdomain/zero/1.0/>.
"""

- xorshift128+ (http://xoroshiro.di.unimi.it/xorshift128plus.c)
"""
  Written in 2014-2016 by Sebastiano Vigna (vigna@acm.org)
  
  To the extent possible under law, the author has dedicated all copyright
  and related and neighboring rights to this software to the public domain
  worldwide. This software is distributed without any warranty.
  
  See <http://creativecommons.org/publicdomain/zero/1.0/>.
"""

- xorshift1024* (http://xoroshiro.di.unimi.it/xorshift1024star.c)
"""
  Written in 2014 by Sebastiano Vigna (vigna@acm.org)
  
  To the extent possible under law, the author has dedicated all copyright
  and related and neighboring rights to this software to the public domain
  worldwide. This software is distributed without any warranty.
  
  See <http://creativecommons.org/publicdomain/zero/1.0/>.
"""