everybody can copy and redistribute with or without alterations, for profit or not, the material published under this licence,

each copy of the material, even if modified, must be redistributed under the same licence, an unabridged copy of the licence must always be included in the distributed document,

in case somebody needs to reproduce a great number of modified copies, they must be available also under a “transparent” form which should easily enable future modifications,

the authors of a previous version must be indicated and the "invariant sections", outlined by the original author and concerning his relation with the document, may under no condition be changed,

if the document is changed, its title must be changed (unless differently indicated by the author).