diff --git a/test/0x.js.ts b/test/0x.js.ts
index 7216ed34f4..9783e69b77 100644
--- a/test/0x.js.ts
+++ b/test/0x.js.ts
@@ -4,6 +4,7 @@ import 'mocha';
 
 describe('ZeroEx library', () => {
     describe('#isValidSignature', () => {
+        // Source: https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_sign
         const data = '0xdeadbeaf';
         const signature = {
             v: 27,