Wording on envelopes...

Does anyone know a website that gives the proper etiquette for the wording on the inner and outer envelopes? Every one I ask gives me a different answer....very frustrating!!!

I need to know for singles with and without guests, couples, and couples with children...

TIA!!!

Cranes website can help. Also I got a little book with my William Arthur invites.

Mr. and Mrs. William Jones (outer)
Mr. and Mrs. Jones (inner)

children go on the inside
Mr. and Mrs. Jones (inner)
Jack and Julie

or
Ms. Jane Jones (outer)
Ms. Jones and Guest (inner)

I found a realy good one but I copyed and pasted it to my email address and I can not get it right on this site
if you want me to email it to you FM me with your email address