Add special requirement for mentioning EVM instructions

EIPS/eip-1.md

@@ -35,6 +35,13 @@ It is highly recommended that a single EIP contain a single key proposal or new
 
 An EIP must meet certain minimum criteria. It must be a clear and complete description of the proposed enhancement. The enhancement must represent a net improvement. The proposed implementation, if applicable, must be solid and must not complicate the protocol unduly.
 
+### Special requirements for Core EIPs
+
+If a **Core** EIP mentions or proposes changes to the EVM (Ethereum Virtual Machine), it should refer to the instructions by their mnemonics and define the opcodes of those mnemonics at least once. A preferred way is the following:
+```
+REVERT (0xfe)
+```
+
 ## EIP Work Flow
 
 Parties involved in the process are you, the champion or *EIP author*, the [*EIP editors*](#eip-editors), and the [*Ethereum Core Developers*](https://github.com/ethereum/pm).