When was the first time the abbreviation "RSA" appeared?

[matqkks]

<Moderator's note: Edited and URL removed due to potential copyright violation.>

When was the first publication of the abbreviation RSA (Rivest, Shamir, Adleman) because it does not appear in an article by Martin Gardner of 1977.

 

[fresh_42]

My bet is $\leq 1983$ since the alternative $US4405829 (A)$ is definitely too bulky.