[docs] Fix a few link issues

docs/data/material/getting-started/overview/overview.md

@@ -22,7 +22,7 @@ You can follow [this GitHub issue](https://github.com/mui/material-ui/issues/293
 
 ## Advantages of Material UI
 
-- **Ship faster:** thousands of open-source [contributors](https://api7.ai/contributor-graph?chart=contributorOverTime&repo=mui-org/material-ui) have poured countless hours into these components.
+- **Ship faster:** Over 2,500 open-source [contributors](https://github.com/mui/material-ui/graphs/contributors) have poured countless hours into these components.
   Focus on your core business logic instead of reinventing the wheel—we've got your UI covered.
 - **Beautiful by default:** we're meticulous about our implementation of [Material Design](https://material.io/), ensuring that every Material UI component meets the highest standards of form and function,
   but diverge from the official spec where necessary to provide multiple great options.

docs/data/system/getting-started/overview/overview.md

@@ -26,5 +26,5 @@ Learn more on [the `sx` prop page](/system/getting-started/the-sx-prop/).
 
 [MUI Base](/base/getting-started/overview/) is a library of "unstyled" React components, while MUI System is a set of utilities for quickly applying styles to those components (as well as other MUI component libraries like Material UI and Joy UI).
 
-MUI Base is a standalone component library, whereas the System is _supplemental_ in that it's designed to be paired with Base and other MUI components, as well as third-party components.
+MUI Base is a standalone component library, whereas MUI System is _supplemental_ in that it's designed to be paired with MUI Base and other MUI components, as well as third-party components.
 See the [Custom components page](/system/getting-started/custom-components/) for details on how to use MUI System with non-MUI components.

docs/data/system/getting-started/usage/usage.md

@@ -148,7 +148,7 @@ It works with both Emotion and styled-components.
   The initial bundle size cost is fixed—it doesn't get any larger as you add more CSS properties.
   You pay the cost of [@emotion/react](https://bundlephobia.com/package/@emotion/react) and [@mui/system](https://bundlephobia.com/package/@mui/system).
   The total size is ~15 kB gzipped.
-  But if you are already using a Core component library like Material UI, then it comes with no extra overhead.
+  But if you are already using an MUI Core component library like Material UI, then it comes with no extra overhead.
 
 #### Cons
 

docs/pages/blog/material-ui-v4-is-out.md

@@ -276,7 +276,7 @@ export default function Hook() {
 ⚠️ Be aware of the difference between _@mui/styles_ and _@mui/material/styles_. The latter contains the [default theme](/material-ui/customization/default-theme/#material-ui-core-styles-vs-material-ui-styles).
 
 - A well supported [Gatsby plugin](https://github.com/hupe1980/gatsby-plugin-material-ui) for _@mui/styles_.
-- A [Cookbook](https://www.amazon.com/gp/product/1789615224/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=1789615224&linkCode=as2&tag=oliviertassin-20&linkId=79aec1cb9db829135838614ac1953380) published by Packt and written by Adam Boduch.
+- A [Cookbook](https://www.packtpub.com/product/react-material-ui-cookbook/9781789615227) published by Packt and written by Adam Boduch.
 
 ![cookbook](/static/blog/material-ui-v4-is-out/cookbook.png)