diff --git a/README.md b/README.md
index a8027c9..a70fc2e 100755
--- a/README.md
+++ b/README.md
@@ -1,12 +1,12 @@
-# Introduction
+### core-js@2.6.12: core-js@<3.4 is no longer maintained and not recommended for usage due to the
+number of issues. Because of the V8 engine whims, feature detection in old core-js versions could cause a slowdown up to 100x even if nothing is polyfilled. Please, upgrade your dependencies to the actual version of core-js.
+```shell
+core-js 버전 3.3 미만은 유지보수가 안되니 사용하지 말라
+# yarn add core-js@^3
 
-This is material design template created based on materially structure
 
-# Getting Started
+# yarn audit  
 
-1. Installation process
-   - run 'npm install / yarn'
-   - start dev server run 'npm run start / yarn start'
-2. Deployment process
-   - Goto full-version directory and open package.json. Update homepage URL to the production URL
-   - Goto full-version directory and run 'npm run build / yarn build'
+# yarn add yarn-audit-fix -D
+# npx yarn-audit-fix
+```
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