diff --git a/lib/sof/all.rb b/lib/sof/all.rb
index 841fa004..97f9986e 100644
--- a/lib/sof/all.rb
+++ b/lib/sof/all.rb
@@ -1,11 +1,11 @@
 require_relative "util"
+require_relative "node"
 require_relative "members"
 require_relative "volotile"
 require_relative "writer"
 require_relative "array"
 require_relative "hash"
 require_relative "occurence"
-require_relative "node"
 
 Symbol.class_eval do
   def to_sof()
diff --git a/lib/sof/array.rb b/lib/sof/array.rb
index a91878cc..64193614 100644
--- a/lib/sof/array.rb
+++ b/lib/sof/array.rb
@@ -1,15 +1,7 @@
-Array.class_eval do
-  def to_sof_node(writer , level)
-    node = Sof::ArrayNode.new()
-    each do |object|
-      node.add writer.to_sof_node( object , level + 1)
-    end
-    node
-  end
-end
 module Sof
   class ArrayNode < Node
-    def initialize 
+    def initialize ref
+      super(ref)
       @children = []
     end
     attr_reader  :children
@@ -17,6 +9,7 @@ module Sof
       @children << c
     end
     def out io , level = 0
+      super
       long_out(io , level)
     end
     
@@ -30,4 +23,13 @@ module Sof
       end
     end
   end
-end
\ No newline at end of file
+end
+Array.class_eval do
+  def to_sof_node(writer , level , ref )
+    node = Sof::ArrayNode.new(ref)
+    each do |object|
+      node.add writer.to_sof_node( object , level + 1)
+    end
+    node
+  end
+end
diff --git a/lib/sof/hash.rb b/lib/sof/hash.rb
index 963b2f0c..93b2c58e 100644
--- a/lib/sof/hash.rb
+++ b/lib/sof/hash.rb
@@ -1,6 +1,7 @@
 module Sof
   class HashNode < Node
-    def initialize 
+    def initialize ref
+      super(ref)
       @children = []
     end
     attr_reader  :children
@@ -8,6 +9,7 @@ module Sof
       @children << [key,val]
     end
     def out io , level = 0
+      super
       indent = " " * level
       @children.each_with_index do |child , i|
         key , val = child
@@ -22,8 +24,8 @@ module Sof
 end
 
 Hash.class_eval do
-  def to_sof_node(writer , level)
-    node = Sof::HashNode.new()
+  def to_sof_node(writer , level , ref)
+    node = Sof::HashNode.new(ref)
     each do |key , object|
       k = writer.to_sof_node( key ,level + 1)
       v = writer.to_sof_node( object ,level +1)
diff --git a/lib/sof/members.rb b/lib/sof/members.rb
index 33d0ff15..188f324d 100644
--- a/lib/sof/members.rb
+++ b/lib/sof/members.rb
@@ -7,15 +7,17 @@ module Sof
       @root = root
       @counter = 1
       @objects = {}
+      @referenced = false
       add(root , 0)
     end
-    attr_reader :objects , :root
+    attr_reader :objects , :root , :referenced
     
     def add object , level
       return if is_value?(object)
       if( occurence = @objects[object] )
         #puts "reset level #{level} at #{occurence.level}"
         occurence.level = level if occurence.level > level
+        occurence.referenced = true
         return
       end
       o = Occurence.new( object , @counter , level )
diff --git a/lib/sof/node.rb b/lib/sof/node.rb
index d7c8307c..88c42409 100644
--- a/lib/sof/node.rb
+++ b/lib/sof/node.rb
@@ -2,16 +2,22 @@
 
 module Sof
   #abstract base class for nodes in the tree
+  # may be referenced (should be a simple name or number)
   class Node
+    def initialize referenced
+      @referenced = referenced
+    end
     include Util
     # must be able to output to a stream
     def out io ,level
-      raise "abstract #{self}"
+      io.write "&#{referenced} " if referenced
     end
+    attr_reader :referenced
   end
   
   class SimpleNode < Node
     def initialize data
+      super(nil)
       @data = data
     end
     attr_reader :data
@@ -21,7 +27,8 @@ module Sof
   end
   
   class ObjectNode < Node
-    def initialize data
+    def initialize data , ref
+      super(ref)
       @data = data 
       @children = []
     end
@@ -30,6 +37,7 @@ module Sof
       @children << [k,v]
     end
     def out io , level = 0
+      super
       io.write(@data)
       indent = " " * (level + 1)
       @children.each_with_index do |child , i|
diff --git a/lib/sof/occurence.rb b/lib/sof/occurence.rb
index 2493ce94..8fc99481 100644
--- a/lib/sof/occurence.rb
+++ b/lib/sof/occurence.rb
@@ -7,7 +7,7 @@ module Sof
       @level = level
     end
     attr_reader   :object , :number
-    attr_accessor :level
+    attr_accessor :level , :referenced
   end
 
 end
diff --git a/lib/sof/writer.rb b/lib/sof/writer.rb
index 3220749a..047d8a51 100644
--- a/lib/sof/writer.rb
+++ b/lib/sof/writer.rb
@@ -22,19 +22,20 @@ module Sof
         #puts "level #{level} at #{occurence.level}"
         return SimpleNode.new("*#{occurence.number}")
       end
+      ref = occurence.referenced ? occurence.number : nil
       if(object.respond_to? :to_sof_node) #mainly meant for arrays and hashes
-        object.to_sof_node(self , level )
+        object.to_sof_node(self , level , ref )
       else
-        object_sof_node(object , level )
+        object_sof_node(object , level , ref )
       end
     end
 
-    def object_sof_node( object , level)
+    def object_sof_node( object , level , ref)
       head = object.class.name + "("
       atts = attributes_for(object)
       immediate , extended = atts.partition {|a| is_value?(get_value(object , a) ) }
       head += immediate.collect {|a| "#{a}: #{get_value(object , a).to_sof()}"}.join(", ") + ")"
-      node = ObjectNode.new(head)
+      node = ObjectNode.new(head , ref)
       extended.each do |a|
         val = get_value(object , a)
         node.add( to_sof_node(a,level + 1) , to_sof_node(val, level + 1) )
diff --git a/test/sof.rb b/test/sof.rb
index 2636d7b2..d86b296b 100644
--- a/test/sof.rb
+++ b/test/sof.rb
@@ -78,12 +78,12 @@ class BasicSof < MiniTest::Test
     ar = [true, 1 ]
     ar << ar
     @out = Sof::Writer.write(ar)
-    check "-true\n-1\n-*1" 
+    check "&1 -true\n-1\n-*1" 
   end
   def test_object_recursive
     object = ObjectWithAttributes.new
     object.extra = object
     @out = Sof::Writer.write(object)
-    check "#{OBJECT_STRING}\n :extra *1" 
+    check "&1 #{OBJECT_STRING}\n :extra *1" 
   end
 end
\ No newline at end of file