On the very first Christmas card was written "A Merry Christmas and a Happy New Year..." http://www.phrases.org.uk/meanings/christmas-card-sayings-and-phrases.html
In wiki dictionary that same general phrase is "Merry Christmas and a Happy New Year" http://en.wiktionary.org/wiki/Merry_Christmas_and_a_Happy_New_Year
However few quick searches in Google show many people use it without any articles like so:
"Merry Christmas and Happy New Year"
So ... does anyone have a source explaining if one of those phrases is "most" correct and if there's any difference implied by the number of articles used?
Edit: Just to make it more clear - I'm asking for the case when you for example design a Christmas card and you have to write the phrase on the card - not personally to anybody, but rather as an impersonally commercial message to the general audience ...