diff --git a/library/network/protocol/content_negotiation/src/implementation/fitness_and_quality.e b/library/network/protocol/content_negotiation/src/implementation/fitness_and_quality.e
index 0b7ab39f..01b38c1f 100644
--- a/library/network/protocol/content_negotiation/src/implementation/fitness_and_quality.e
+++ b/library/network/protocol/content_negotiation/src/implementation/fitness_and_quality.e
@@ -1,5 +1,5 @@
 note
-	description: "Summary description for {FITNESS_AND_QUALITY}."
+	description: "FITNESS_AND_QUALITY. Object holding a fitness/quality values."
 	date: "$Date$"
 	revision: "$Revision$"
 
@@ -20,6 +20,7 @@ create
 feature -- Initialization
 
 	make (a_fitness: INTEGER; a_quality: REAL_64)
+			-- Create an object with `a_fitness' and `a_quality'
 		do
 			fitness := a_fitness
 			quality := a_quality
@@ -27,6 +28,7 @@ feature -- Initialization
 		ensure
 			fitness_assigned : fitness = a_fitness
 			quality_assigned : quality = a_quality
+			entity_empty: entity.is_empty
 		end
 
 feature -- Access
diff --git a/library/network/protocol/content_negotiation/src/results/http_accept_language.e b/library/network/protocol/content_negotiation/src/results/http_accept_language.e
index 9b6b9be9..74729711 100644
--- a/library/network/protocol/content_negotiation/src/results/http_accept_language.e
+++ b/library/network/protocol/content_negotiation/src/results/http_accept_language.e
@@ -7,6 +7,8 @@ class
 	HTTP_ACCEPT_LANGUAGE
 
 inherit
+	HTTP_HEADER_UTILITIES
+
 	REFACTORING_HELPER
 
 	DEBUG_OUTPUT
@@ -222,16 +224,6 @@ feature {NONE} -- Implementation
 			end
 		end
 
-feature {NONE} -- Helper
-
-	trimmed_string (s: READABLE_STRING_8): STRING_8
-			-- Copy of `s', where whitespace were stripped from the beginning and end of the string
-		do
-			create Result.make_from_string (s)
-			Result.left_adjust
-			Result.right_adjust
-		end
-
 invariant
 	valid_quality: 0.0 <= quality and quality <= 1.0
 
diff --git a/library/network/protocol/content_negotiation/src/results/http_any_accept.e b/library/network/protocol/content_negotiation/src/results/http_any_accept.e
index f35bbb4d..71a41f2e 100644
--- a/library/network/protocol/content_negotiation/src/results/http_any_accept.e
+++ b/library/network/protocol/content_negotiation/src/results/http_any_accept.e
@@ -7,6 +7,8 @@ class
 	HTTP_ANY_ACCEPT
 
 inherit
+	HTTP_HEADER_UTILITIES
+
 	REFACTORING_HELPER
 
 	DEBUG_OUTPUT
@@ -101,16 +103,6 @@ feature -- Status Report
 			create Result.make_from_string (value)
 		end
 
-feature {NONE} -- Helper
-
-	trimmed_string (s: READABLE_STRING_8): STRING_8
-			-- Copy of `s', where whitespace were stripped from the beginning and end of the string
-		do
-			create Result.make_from_string (s)
-			Result.left_adjust
-			Result.right_adjust
-		end
-
 note
 	copyright: "2011-2013, Javier Velilla, Jocelyn Fiat, Eiffel Software and others"
 	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
diff --git a/library/network/protocol/content_negotiation/src/variants/http_accept_charset_variants.e b/library/network/protocol/content_negotiation/src/variants/http_accept_charset_variants.e
index 3a36e0a8..13775ebd 100644
--- a/library/network/protocol/content_negotiation/src/variants/http_accept_charset_variants.e
+++ b/library/network/protocol/content_negotiation/src/variants/http_accept_charset_variants.e
@@ -24,6 +24,7 @@ create
 feature -- Change
 
 	set_vary_header_value
+			-- <Precursor>
 		do
 			vary_header_value := {HTTP_HEADER_NAMES}.header_accept_charset -- "Accept-Charset"
 		end
diff --git a/library/network/protocol/content_negotiation/src/variants/http_accept_encoding_variants.e b/library/network/protocol/content_negotiation/src/variants/http_accept_encoding_variants.e
index 805bf1a9..d814d5fc 100644
--- a/library/network/protocol/content_negotiation/src/variants/http_accept_encoding_variants.e
+++ b/library/network/protocol/content_negotiation/src/variants/http_accept_encoding_variants.e
@@ -24,6 +24,7 @@ create
 feature -- Change
 
 	set_vary_header_value
+			-- <Precursor>
 		do
 			vary_header_value := {HTTP_HEADER_NAMES}.header_accept_encoding -- "Accept-Encoding"
 		end
diff --git a/library/network/protocol/content_negotiation/src/variants/http_accept_language_variants.e b/library/network/protocol/content_negotiation/src/variants/http_accept_language_variants.e
index f51b1f87..78320048 100644
--- a/library/network/protocol/content_negotiation/src/variants/http_accept_language_variants.e
+++ b/library/network/protocol/content_negotiation/src/variants/http_accept_language_variants.e
@@ -23,6 +23,7 @@ create
 feature -- Change
 
 	set_vary_header_value
+			-- <Precursor>
 		do
 			vary_header_value := {HTTP_HEADER_NAMES}.header_accept_language -- "Accept-Language"
 		end
diff --git a/library/network/protocol/content_negotiation/src/variants/http_accept_media_type_variants.e b/library/network/protocol/content_negotiation/src/variants/http_accept_media_type_variants.e
index 00900ce3..1f15ce31 100644
--- a/library/network/protocol/content_negotiation/src/variants/http_accept_media_type_variants.e
+++ b/library/network/protocol/content_negotiation/src/variants/http_accept_media_type_variants.e
@@ -23,6 +23,7 @@ create
 feature -- Change
 
 	set_vary_header_value
+			-- <Precursor>
 		do
 			vary_header_value := {HTTP_HEADER_NAMES}.header_accept -- "Accept"
 		end