Patent Cooperation Treaty (PCT) and Regulations Under The PCT: Done at Washington on June 19, 1970, Amended on September 28, 1979, Modified on February ... From April 1, 20 (Wipo Publication Number) Patent Cooperation Treaty (PCT) and Regulations Under The PCT: Done at Washington on June 19, 1970, Amended on September 28, 1979, Modified on February ... From April 1, 20 (Wipo Publication Number)