Chinese Constitution in 1969 - Page 11
Chapter IV -- Central Organizations of the Party

Article 8

The National Party Congress shall be convened every five years. Under special circumstances, it may be convened before its due date or postponed.

Article 9

The plenary session of the Central Committee of the Party elects the Political Bureau of the Central Committee, the Standing Committee of the Political Bureau of the Central Committee and the Chairman and Vice-Chairman of the Central Committee.

The plenary session of the Central Committee of the Party is convened by the Political Bureau of the Central Committee.
When the Central Committee is not in plenary session, the Political Bureau of the Central Committee and its Standing Committee exercise the functions and powers of the Central Committee.

Under the leadership of the Chairman, the Vice-Chairman and the Standing Committee of the Political Bureau of the Central Committee, a number of necessary organs which are compact and efficient, shall be set up to attend to the day-to-day work of the Party, the government and the army in a centralized way.