diff --git a/_SUMMARY.md b/_SUMMARY.md
index c5fdcd887..82bfaaf09 100644
--- a/_SUMMARY.md
+++ b/_SUMMARY.md
@@ -94,9 +94,7 @@
 * [SDK](reference_guide/project_model/sdk.md)
 * [Library](reference_guide/project_model/library.md)
 * [Facet](reference_guide/project_model/facet.md)
-* [Build System](reference_guide/project_model/build_system.md)
-    * [External Builder API and Plugins](reference_guide/frameworks_and_external_apis/external_builder_api.md)
-    * [External system integration](reference_guide/frameworks_and_external_apis/external_system_integration.md)
+* [External system integration](reference_guide/frameworks_and_external_apis/external_system_integration.md)
 
 ## Part IV - PSI
 * [What is the PSI?](basics/architectural_overview/psi.md)
@@ -136,6 +134,8 @@
 * Project View
     * [Modifying Project View Structure](tutorials/tree_structure_view.md)
 * Unit Testing
+* [Build System](reference_guide/project_model/build_system.md)
+    * [External Builder API and Plugins](reference_guide/frameworks_and_external_apis/external_builder_api.md)
 
 ## Part VI - Testing
 
diff --git a/reference_guide/frameworks_and_external_apis/external_system_integration.md b/reference_guide/frameworks_and_external_apis/external_system_integration.md
index 00c29e7df..c06cd72ac 100644
--- a/reference_guide/frameworks_and_external_apis/external_system_integration.md
+++ b/reference_guide/frameworks_and_external_apis/external_system_integration.md
@@ -76,12 +76,3 @@ It's recommended to extend from [AbstractExternalProjectSettingsControl](upsourc
 Similar approach is used for providing 'import from external system' UI - implementation is expected to extended [AbstractImportFromExternalSystemControl](upsource:///platform/external-system-impl/src/com/intellij/openapi/externalSystem/service/settings/AbstractImportFromExternalSystemControl.java) and it has not linked external projects list but target external project path control:
 
 ![Import from external system](/reference_guide/img/import.png)
-
-# Using with 12.1.x IJ branch
-
-Though main development is performed at the 'master' branch, there is a special 12.1.x-compatible version. Here are instructions on how to use it:
-
-1.  Download external-system.zip;
-2.  Unpack it and define *external-system.jar* as a library dependency;
-3.  Configure sources from *external-system-src.jar* if necessary;
-4.  Add definitions from *ExternalSystemExtensionPoints.xml* and *ExternalSystemExtensions.xml* to your *plugin.xml* (that **.xml files are bundled into *external-system-src.jar*). *Note:** it's very important to use custom namespace there because there is a possible case that more than one external system integration uses this approach to be compatible with 12.1.x;
diff --git a/reference_guide/project_model/build_system.md b/reference_guide/project_model/build_system.md
index 946fe1b07..1f07ce82a 100644
--- a/reference_guide/project_model/build_system.md
+++ b/reference_guide/project_model/build_system.md
@@ -3,4 +3,3 @@ title: Build System
 ---
 
 * [External builder API and plugins](/reference_guide/frameworks_and_external_apis/external_builder_api.md)
-* [External system integration](/reference_guide/frameworks_and_external_apis/external_system_integration.md)