Article 166
Accession

(1) This Convention shall be open to accession by: 

(a) the States referred to in Article 165, paragraph 1;

(b) any other European State at the invitation of the Administrative Council. 

(2) Any State which has been a party to the Convention and has ceased to be so as a result of the application of Article 172, paragraph 4, may again become a party to the Convention by acceding to it.

(3) Instruments of accession shall be deposited with the Government of the Federal Republic of Germany.