A study of the social systems of push pins.
Contributed and licensed under the GFDL by the photographer,
Gregory Maxwell.
I, the copyright holder of this work, hereby publish it under the following license:
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 only as published by the
Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.