1978-05-31 /bb-d868a-bm/01/3-documentation/qt022.dd 1978-09-14 /bb-d868b-bm_tops20_v3a_2020_dist/01/3a-documentation/qt022.dd 1980-03-17 /BB-D868C-BM/01/4-documentation/qt022.dd 1980-03-17 /BB-D868D-BM/01/4-documentation/qt022.dd 1980-03-17 /bb-d868c-bm_tops20_v4_2020_distr/01/4-documentation/qt022.dd