A lot of sites just say "Enscribed at Thermopylae" on a stone or whatever.
I only saw one webpage that said "attributed."
Most everyone seems to give it solidly to Simonides.
http://members.netnormal.com/library/leonidas.htm
http://www.spartans-fc.com/News/histroy1.htm
Go tell the Spartans, stranger passing by, that here obedient to their laws we lie.
~Simonides - Epitath on the monument marking the Battle of Thermopylae
http://www.iconian.com/quotes2.html
The full quote is given by Simonides (5th century BC) as:
"Go, tell the Spartans, thou who passest by,
That here obedient to their laws we lie"
http://www.cs.hut.fi/~pno/Fiction/apf/a ... amids.html
THERMOPYLAE
Go tell the Spartans, thou that passest by,
That here, obedient to their laws, we lie.
~Simonides, Tr. William Lisle Bowels
http://www.glaced.digitalspace.net/cgi- ... pylae.html
An epitaph to commemorate the heroic last stand at Thermopylae was written by Simonides: "Go tell the Spartans, thou who passest by, that here obedient to their laws we lie."
http://www.geocities.com/Athens/Acropol ... stands.htm