diff --git a/Sources/HTMLDOMUtils.h b/Sources/HTMLDOMUtils.h
index fba89a6..2b62d59 100644
--- a/Sources/HTMLDOMUtils.h
+++ b/Sources/HTMLDOMUtils.h
@@ -7,7 +7,8 @@
 //
 
 #import <Foundation/Foundation.h>
+#import "HTMLDOM.h"
 
-@interface HTMLDOMUtils : NSObject
+@class HTMLNode;
 
-@end
+extern HTMLNode * GetCommonAncestorContainer(HTMLNode *nodeA, HTMLNode *nodeB);
diff --git a/Sources/HTMLDOMUtils.m b/Sources/HTMLDOMUtils.m
index 7ab2d01..45a95ef 100644
--- a/Sources/HTMLDOMUtils.m
+++ b/Sources/HTMLDOMUtils.m
@@ -7,7 +7,17 @@
 //
 
 #import "HTMLDOMUtils.h"
+#import "HTMLNode.h"
 
-@implementation HTMLDOMUtils
+extern HTMLNode * GetCommonAncestorContainer(HTMLNode *nodeA, HTMLNode *nodeB)
+{
+	for (HTMLNode *parentA = nodeA; parentA != nil; parentA = parentA.parentNode) {
+		for (HTMLNode *parentB = nodeB; parentB != nil; parentB = parentB.parentNode) {
+			if (parentA == parentB) {
+				return parentA;
+			}
+		}
+	}
 
-@end
+	return nil;
+}