MS-DOS 1.25 source code (SCP OEM) released by CHM. Timestamps provided below for reference:
1983/05/09 09:59:14 63,781 ASM.ASM
1983/05/17 18:19:00 67,064 COMMAND.ASM
1982/07/02 11:33:26 3,625 HEX2BIN.ASM
1982/08/03 00:29:18 36,882 IO.ASM
1983/05/17 18:15:22 114,253 MSDOS.ASM
1983/05/17 18:20:16 649 STDDOS.ASM
1982/07/01 23:54:50 16,223 TRANS.ASM