fix some 404 errors

content/en/docs/concepts/extend-kubernetes/api-extension/custom-resources.md

@@ -108,11 +108,11 @@ Use a custom resource (CRD or Aggregated API) if most of the following apply:
 Kubernetes provides two ways to add custom resources to your cluster:
 
 - CRDs are simple and can be created without any programming.
-- [API Aggregation](/docs/concepts/api-extension/apiserver-aggregation/) requires programming, but allows more control over API behaviors like how data is stored and conversion between API versions.
+- [API Aggregation](/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/) requires programming, but allows more control over API behaviors like how data is stored and conversion between API versions.
 
 Kubernetes provides these two options to meet the needs of different users, so that neither ease of use nor flexibility is compromised.
 
-Aggregated APIs are subordinate APIServers that sit behind the primary API server, which acts as a proxy. This arrangement is called [API Aggregation](/docs/concepts/api-extension/apiserver-aggregation/) (AA). To users, it simply appears that the Kubernetes API is extended.
+Aggregated APIs are subordinate APIServers that sit behind the primary API server, which acts as a proxy. This arrangement is called [API Aggregation](/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/) (AA). To users, it simply appears that the Kubernetes API is extended.
 
 CRDs allow users to create new types of resources without adding another APIserver. You do not need to understand API Aggregation to use CRDs.
 
@@ -138,7 +138,7 @@ CRD is the successor to the deprecated *ThirdPartyResource* (TPR) API, and is av
 
 Usually, each resource in the Kubernetes API requires code that handles REST requests and manages persistent storage of objects. The main Kubernetes API server handles built-in resources like *pods* and *services*, and can also handle custom resources in a generic way through [CRDs](#customresourcedefinitions).
 
-The [aggregation layer](/docs/concepts/api-extension/apiserver-aggregation/) allows you to provide specialized
+The [aggregation layer](/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/) allows you to provide specialized
 implementations for your custom resources by writing and deploying your own standalone API server.
 The main API server delegates requests to you for the custom resources that you handle,
 making them available to all of its clients.

content/en/docs/concepts/extend-kubernetes/service-catalog.md

@@ -32,7 +32,7 @@ The application can simply use it as a service.
 
 Service Catalog uses the [Open service broker API](https://github.com/openservicebrokerapi/servicebroker) to communicate with service brokers, acting as an intermediary for the Kubernetes API Server to negotiate the initial provisioning and retrieve the credentials necessary for the application to use a managed service.
 
-It is implemented as an extension API server and a controller, using etcd for storage. It also uses the [aggregation layer](/docs/concepts/api-extension/apiserver-aggregation/) available in Kubernetes 1.7+ to present its API.
+It is implemented as an extension API server and a controller, using etcd for storage. It also uses the [aggregation layer](/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/) available in Kubernetes 1.7+ to present its API.
 
 <br>
 

content/en/docs/tasks/access-kubernetes-api/configure-aggregation-layer.md

@@ -10,7 +10,7 @@ weight: 10
 
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-Configuring the [aggregation layer](/docs/concepts/api-extension/apiserver-aggregation/) allows the Kubernetes apiserver to be extended with additional APIs, which are not part of the core Kubernetes APIs. 
+Configuring the [aggregation layer](/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/) allows the Kubernetes apiserver to be extended with additional APIs, which are not part of the core Kubernetes APIs. 
 
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