RETAINED RIGHTS/TERMS AND CONDITIONS
1. Authors/employers retain all proprietary rights in any process, procedure, or article of manufacture described in the Work.
...
6. Although authors are permitted to re-use all or portions of the Work in other works, this does not include granting third-party requests for reprinting, republishing, or other types of re-use. The IEEE Intellectual Property Rights office must handle all such third-party requests.

當(dāng)然，會議論文如果以書或雜志增刊出版了的話，那就算發(fā)表了，一般不可以再投了（除非有足夠的擴(kuò)充）。比如LNCS里就有寫明，出版社有獨家發(fā)表權(quán)，作者保留的權(quán)利該不大了。

The copyright transfer covers the sole right to print, publish, distribute and sell throughout the world。。。

知網(wǎng)論文查重

如果有一部分內(nèi)容在會議論文集上發(fā)表過，投期刊的時候如何寫cover letter呢？

編輯一般不會細(xì)看coverletter。小部分內(nèi)容重復(fù)，文章里引用前面的會議文章就可以了。若有很多重復(fù)，甚至只是做了小的修改，一般要寫清楚：“An earlier version of this paper was presented at the International Conference"