Cutts, Martin. Oxford Quick Reference Plain English Guide. Oxford: Oxford University Press, 1995.
Cutts, Martin. Oxford Guide to Plain English, Third Edition. Oxford: Oxford University Press, 2009.
European Union. How to write clearly, available in more than 20 languages.
Multiculturalism and Citizenship Canada. Plain Language Clear and Simple. Ottawa: Minister of Supply and Services Canada, 1991.
Stephens, Cheryl, ed. Plain Language in Plain English. Vancouver: Plain Language Wizardry, 2010
U.S. Securities and Exchange Commission: A Plain English Handbook. Washington, D.C., 1998.
Government of Canada: Plain Language, Clear and Simple. You can get a free PDF of this 1991 guide and its 1994 companion guide for trainers on the Clear Communication Wiki at http://clear-communication.wikia.com/wiki/Training. Also available in French.