Treaties and other international acts series. * Paper, $15.00 a yr. (approximately 150 issues), $7.00 additional for foreign mailing; single copies vary in price. 6899. Mutual defense assistance, agreement between United States and Belgium, amending Annex B to agreement of Jan. 27, 1950, effected by exchange of notes signed Brussels May 19 and June 18, 1970; [entered into force June 18, 1970].