"Visually Perceptible Copies
The notice for visually perceptible copies should contain all
three elements described below. They should appear together
or in close proximity on the copies.
1 The symbol © (letter C in a circle); the word “Copyright”;
or the abbreviation “Copr.”
2 The year of first publication. If the work is a derivative
work or a compilation incorporating previously published
material, the year date of first publication of the derivative
work or compilation is sufficient. Examples of derivative
works are translations or dramatizations; an example of
a compilation is an anthology. The year may be omitted when a pictorial, graphic, or sculptural work, with
accompanying textual matter, if any, is reproduced in or
on greeting cards, postcards, stationery, jewelry, dolls, toys,
or useful articles.
3 The name of the copyright owner, an abbreviation by
which the name can be recognized, or a generally known
alternative designation of owner.
Example © 2007 Jane
The “C in a circle” notice is used only on “visually perceptible” copies."
Then send yourself a copy of your artwork to yourself in the mail. Don't open the envelope.