Politburo member and Permanent member of the Communist Party of Viet Nam (CPV) Central Committee’s Secretariat Tran Cam Tu and Vice President of the Cambodian People’s Party (CPP) and Chairman of Standing Board of the CPP Central Committee Say Chhum witnessed the exchange of cooperation documents between the two countries' localities in Phnom Penh on April 10, as part of the former’s official visit to Cambodia.