diff --git a/httpclient/src/main/java/org/apache/http/conn/DnsResolver.java b/httpclient/src/main/java/org/apache/http/conn/DnsResolver.java
index 73cab4439..c4501f39e 100644
--- a/httpclient/src/main/java/org/apache/http/conn/DnsResolver.java
+++ b/httpclient/src/main/java/org/apache/http/conn/DnsResolver.java
@@ -32,6 +32,8 @@ import java.net.UnknownHostException;
 /**
  * Users may implement this interface to override the normal DNS lookup offered
  * by the OS.
+ *
+ * @since 4.2
  */
 public interface DnsResolver {
 
diff --git a/httpclient/src/main/java/org/apache/http/impl/conn/DefaultClientConnectionOperator.java b/httpclient/src/main/java/org/apache/http/impl/conn/DefaultClientConnectionOperator.java
index 49f4235de..46c06fcf6 100644
--- a/httpclient/src/main/java/org/apache/http/impl/conn/DefaultClientConnectionOperator.java
+++ b/httpclient/src/main/java/org/apache/http/impl/conn/DefaultClientConnectionOperator.java
@@ -99,6 +99,8 @@ public class DefaultClientConnectionOperator implements ClientConnectionOperator
      * Creates a new client connection operator for the given scheme registry.
      *
      * @param schemes   the scheme registry
+     *
+     * @since 4.2
      */
     public DefaultClientConnectionOperator(final SchemeRegistry schemes) {
         if (schemes == null) {
diff --git a/httpclient/src/main/java/org/apache/http/impl/conn/InMemoryDnsResolver.java b/httpclient/src/main/java/org/apache/http/impl/conn/InMemoryDnsResolver.java
index d12ad616b..fc06da3e2 100644
--- a/httpclient/src/main/java/org/apache/http/impl/conn/InMemoryDnsResolver.java
+++ b/httpclient/src/main/java/org/apache/http/impl/conn/InMemoryDnsResolver.java
@@ -38,6 +38,8 @@ import org.apache.http.conn.DnsResolver;
 
 /**
  * In-memory DNS resolver implementation.
+ *
+ * @since 4.2
  */
 public class InMemoryDnsResolver implements DnsResolver {
 
diff --git a/httpclient/src/main/java/org/apache/http/impl/conn/SystemDefaultDnsResolver.java b/httpclient/src/main/java/org/apache/http/impl/conn/SystemDefaultDnsResolver.java
index 8ff86aad6..1196d9527 100644
--- a/httpclient/src/main/java/org/apache/http/impl/conn/SystemDefaultDnsResolver.java
+++ b/httpclient/src/main/java/org/apache/http/impl/conn/SystemDefaultDnsResolver.java
@@ -34,6 +34,7 @@ import org.apache.http.conn.DnsResolver;
 /**
  * DNS resolver that uses the default OS implementation for resolving host names.
  *
+ * @since 4.2
  */
 public class SystemDefaultDnsResolver implements DnsResolver {