diff --git a/src/observersmanager.hpp b/src/observersmanager.hpp
index 40d08f3..b5340ef 100644
--- a/src/observersmanager.hpp
+++ b/src/observersmanager.hpp
@@ -20,54 +20,109 @@
 #ifndef idF5E41734950640CDA3C949E0D3A9A30D
 #define idF5E41734950640CDA3C949E0D3A9A30D
 
-#include "linearmap.hpp"
 #include <cassert>
 #include <vector>
 #include <algorithm>
 #include <iterator>
 #include <ciso646>
+#include <tree.hh>
+#include <boost/iterator/transform_iterator.hpp>
 
 namespace cloonel {
 	template <typename T>
 	class ObserversManager {
 	public:
 		typedef size_t TicketType;
-		typedef typename LinearMap<T>::iterator iterator;
-
-		ObserversManager ( void ) = default;
-		~ObserversManager ( void ) noexcept = default;
-
-		TicketType Add ( T parObserver );
-		void Remove ( TicketType parTicket ) noexcept;
-		void Update ( TicketType parTicket, T parObserver );
-		std::size_t size ( void ) const { return m_list.size(); }
-		iterator begin ( void ) { return m_list.begin(); }
-		iterator end ( void ) { return m_list.end(); }
 
 	private:
-		LinearMap<T> m_list;
+		struct TicketedWrapper {
+			TicketedWrapper ( void ) = default;
+			TicketedWrapper ( T parItem, TicketType parTicket ) :
+				itm(parItem),
+				ticket(parTicket)
+			{
+			}
+
+			T itm;
+			TicketType ticket;
+
+			bool operator== ( const TicketedWrapper& parOther ) const { return parOther.ticket == ticket; }
+			bool operator== ( TicketType parOther ) const { return parOther == ticket; }
+		};
+		static T& TicketedWrapperToItm ( TicketedWrapper& parWrapper ) { return parWrapper.itm; }
+
+		typedef tree<TicketedWrapper> TreeType;
+		typedef typename tree<TicketedWrapper>::iterator TreeIteratorType;
+
+	public:
+		enum {
+			Ticket_Null = 0
+		};
+		typedef boost::transform_iterator<std::function<T&(TicketedWrapper&)>, TreeIteratorType> iterator;
+
+		ObserversManager ( void );
+		~ObserversManager ( void ) noexcept = default;
+
+		TicketType Add ( T parObserver, TicketType parParent=Ticket_Null );
+		void Remove ( TicketType parTicket ) noexcept;
+		void Update ( TicketType parTicket, T parObserver );
+		std::size_t size ( void ) const { return m_tree.size(); }
+		iterator begin ( void ) { return iterator(m_tree.begin(), &TicketedWrapperToItm); }
+		iterator end ( void ) { return iterator(m_tree.end(), &TicketedWrapperToItm); }
+
+	private:
+		TreeIteratorType GetByTicket_AssertPresent ( TicketType parTicket );
+
+		TreeType m_tree;
+		TicketType m_nextTicket;
 	};
 
 	///--------------------------------------------------------------------------
 	///--------------------------------------------------------------------------
 	template <typename T>
-	typename ObserversManager<T>::TicketType ObserversManager<T>::Add (T parObserver) {
-		m_list.push_back(parObserver);
-		return static_cast<TicketType>(m_list.size());
+	ObserversManager<T>::ObserversManager() :
+		m_nextTicket(1)
+	{
+	}
+
+	///--------------------------------------------------------------------------
+	///--------------------------------------------------------------------------
+	template <typename T>
+	typename ObserversManager<T>::TicketType ObserversManager<T>::Add (T parObserver, TicketType parParent) {
+		const auto currTicket = m_nextTicket;
+		if (Ticket_Null == parParent)
+			m_tree.insert(m_tree.begin(), TicketedWrapper(parObserver, currTicket));
+		else
+			m_tree.append_child(GetByTicket_AssertPresent(parParent), TicketedWrapper(parObserver, currTicket));
+
+		++m_nextTicket;
+		return currTicket;
 	}
 
 	///--------------------------------------------------------------------------
 	///--------------------------------------------------------------------------
 	template <typename T>
 	void ObserversManager<T>::Remove (TicketType parTicket) noexcept {
-		m_list.erase_absolute(parTicket - 1);
+		auto deleme = GetByTicket_AssertPresent(parTicket);
+		m_tree.erase(deleme);
+		if (parTicket == m_nextTicket - 1)
+			--m_nextTicket;
 	}
 
 	///--------------------------------------------------------------------------
 	///--------------------------------------------------------------------------
 	template <typename T>
 	void ObserversManager<T>::Update (TicketType parTicket, T parObserver) {
-		std::swap(*m_list.at_absolute(parTicket - 1), parObserver);
+		std::swap(GetByTicket_AssertPresent(parTicket)->itm, parObserver);
+	}
+
+	///--------------------------------------------------------------------------
+	///--------------------------------------------------------------------------
+	template <typename T>
+	typename ObserversManager<T>::TreeIteratorType ObserversManager<T>::GetByTicket_AssertPresent (TicketType parTicket) {
+		auto ret = std::find(m_tree.begin(), m_tree.end(), parTicket);
+		assert(m_tree.end() != ret);
+		return ret;
 	}
 } //namespace cloonel