Correct copyright reference

["Sandro Fergnani" <safe60@...>]

Hi all. This is my first post to the list. I'm using lua to build a 
dedicated language for numerical control. Using the Lua API  I added  many 
custom commands to the lua interpreter. My question is :
Is there a reccomended way to give credtis to LUA ?  I want to place my 
copyright information notice for the part I wrote myself, but I obviously 
want to give credits to the LUA environment. It's enough if I leave the 
original copyright notice untouched and just add my own copyright text ?
Thanks for your opinion.

Sandro