diff --git a/readme.md b/readme.md
index 4b01b2a..966304d 100644
--- a/readme.md
+++ b/readme.md
@@ -55,3 +55,5 @@ deployment cycle. It is a non-configurable module and has the defaults based on
 3. [Asset caching module](https://github.com/ampproject/amp-sw/tree/master/src/modules/asset-caching) is a lazily loaded and optional, it can be used to cache the static assets like images/ fonts etc. You can give the reg-exp for matching assets and the caching strategy(CACHE_FIRST/NETWORK-FIRST/CACHE-ONLY) for the same.
 4. [Offline page module](https://github.com/ampproject/amp-sw/tree/master/src/modules/offline-page) can be used to introduce an offline page to your web app. AMP_SW only caches the documents which the user has already visited. If in the absence of the network the user tries to navigate to a page which is not available in the cache, this offline page is shown as a backup to let the user know what happened.
 5. [Link prefetch module](https://github.com/ampproject/amp-sw/tree/master/src/modules/link-prefetch) provides link prefetch capabilities to the browsers which do not support `link rel=prefetch`. You can use this to prefetch links and serve them from the service worker cache for the next time.
+
+While `amp-sw` is divided into smaller sub modules, the core funationality of this project relies on the [Workbox](https://github.com/GoogleChrome/workbox) project. The `amp-sw` modules also extend parts of the Workbox project.