Self-dual codes overGF(3)andGF(4)of length not exceeding 16

All self-dual codes over GF(3) and GF(4) of length 16 are found. The self-dual codes of shorter length are described in a concise and systematic notation. A number of new techniques ("promotion" and "demotion," "tag olng? and "subtraction") are given for constructing codes. Finally, several new extremal self-dual codes are given which have length greater than 16.