I propose replacing STOP with 0 in lines 2411 and 2433 of Paper.tex, which discribe the 0x39 & 0x3c opcodes.

Rationale:

• Meaning: STOP and 0 are equivalent in this context, but 0 is more unambiguous.
• Consistency: 0 used in the descriptions 0x37 and 0x3e opcodes.