i am not sure this is enough. (otherwise the FSF would handle it this way too.
an interresting paper to read on this topic is: http://www.ifross.de/ifross_html/art30.pdf
in particular it explains that for countries that have a system similar to the german urrheberrecht (which are all european countries except great britain) it is not enough to simply assign all rights (because not all rights can be assigned). therefore it is necessary to specifically mention each right that is to be assigned because any such contract is to be interpreted as restrictive as possible in favour of the original author. it is also necessary to clearly state which rights stay with the author to make sure the contract stays valid. (if the contract has invalid parts, all may be lost)
unfortunately it's in german.
there maybe more on: http://www.ifross.de/
greetings, martin.