EFFECT OF ENTRY INTO FORCE
Any State which becomes a Party to, the Single Convention after the entry into force of this Protocol pursuant to paragraph 1 of article 18 above shall, failing an expression of a different intention by that State:
(a) Be considered as a Party to the Single Convention as amended;
(b) Be considered as a Party to the unamended Single Convention in relation to any Party to that Convention not bound by this Protocol.
Article 19 accords with and follows closely the text of article 40, paragraph 5, of the Vienna Convention on the Law of Treaties.'
1 Document A/CONF.39/27. Article 40, paragraph 5 of that Convention reads as follows:
"5. Any State which becomes a party to the treaty after the entry into force of the amending agreement shall, failing an expression of a different intention by that State:
"(a) be considered as a party to the treaty as amended; and
"(b) be considered as a party to the unamended treaty in relation to any party to the treaty not bound by the amending agreement."