The People's Republic of China issued its first round of official character simplifications in two documents, the first in 1956 and the second in 1964. A second round of character simplifications (known as erjian, or "second round simplified characters") was promulgated in 1977. It was poorly received, and in 1986 the authorities rescinded the second round completely, while making six revisions to the 1964 list, including the restoration of three traditional characters that had been simplified: 叠 dié, 覆 fù, 像 xiàng.

Who issued its first round of character simplifications in two documents?