Complex sentence: The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959, namely the United States, United Kingdom, Canada, Australia, New Zealand and South Africa.
Split into simpler sentences: The international yard and pound are two units of measurement that were the subject of an agreement between six nations signed on 1 July 1959. The six nations were the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa.