Added Licence details

Updated line #33 with licence details require to have OATH Hardware token.

Author: shwetamathur7

articles/active-directory/authentication/concept-authentication-oath-tokens.md

@@ -30,7 +30,7 @@ Some OATH TOTP hardware tokens are programmable, meaning they don't come with a
 
 ## OATH hardware tokens (Preview)
 
-Azure AD supports the use of OATH-TOTP SHA-1 tokens that refresh codes every 30 or 60 seconds. Customers can purchase these tokens from the vendor of their choice. 
+Azure AD supports the use of OATH-TOTP SHA-1 tokens that refresh codes every 30 or 60 seconds. Customers can purchase these tokens from the vendor of their choice. Hardware OATH tokens are available for users with an Azure AD Premium P1 or P2 license.  
 
 OATH TOTP hardware tokens typically come with a secret key, or seed, pre-programmed in the token. These keys must be input into Azure AD as described in the following steps. Secret keys are limited to 128 characters, which may not be compatible with all tokens. The secret key can only contain the characters *a-z* or *A-Z* and digits *2-7*, and must be encoded in *Base32*.