diff --git a/core/filter.cpp b/core/filter.cpp
index f39c3ebe..5956a758 100644
--- a/core/filter.cpp
+++ b/core/filter.cpp
@@ -1,4 +1,4 @@
-/**
+/*
  * Copyright 2013 (c) Anna Schumaker.
  */
 
@@ -9,7 +9,6 @@ extern "C" {
 #include <core/string.h>
 }
 
-#include <algorithm>
 
 static struct database filter_index;
 
diff --git a/include/core/filter.h b/include/core/filter.h
index 78d8ce8c..0e440e8d 100644
--- a/include/core/filter.h
+++ b/include/core/filter.h
@@ -1,5 +1,8 @@
-/**
+/*
  * Copyright 2013 (c) Anna Schumaker.
+ *
+ * The filter layer is used to search for a subset of
+ * songs based on an input string.
  */
 #ifndef OCARINA_CORE_FILTER_H
 #define OCARINA_CORE_FILTER_H
@@ -8,32 +11,11 @@ extern "C" {
 #include <core/set.h>
 }
 
-#include <string>
-
-/**
- * The filter layer is used to find a subset of songs based on an input
- * string.  Since this layer does text processing, it also provides a
- * functions for converting strings to lowercase.
- *
- * The text processing is mostly interested in alphanumeric characters, so
- * any special characters included in the input text will be stripped out.
- * Tabs, spaces and the following characters are used to delimit words:
- *
- * 	\/,;()_-~+"
- */
-namespace filter {
-
-	/**
-	 * Converts the input text to lowercase and returns the result.
-	 *
-	 * @param  text  The text to be converted.
-	 * @return The lowercase form of the input text.
-	 */
-	std::string lowercase(const std::string &);
-
-};
 
+/* Called to initialize the filter index. */
 void filter_init();
+
+/* Called to clean up the filter index. */
 void filter_deinit();
 
 /* Add the input string to the index. */