diff -r fb60f631790b -r 9ffff9051a4b lemon/preflow.h
--- a/lemon/preflow.h	Sun Sep 16 13:29:42 2007 +0000
+++ b/lemon/preflow.h	Sun Sep 16 14:21:12 2007 +0000
@@ -210,6 +210,8 @@
     ///minCut returns a minimum cut.     
     ///\warning \ref minMinCut and \ref maxMinCut do not give minimum
     ///value cuts unless calling \ref phase2.  
+    ///\warning A real flow map (i.e. not \ref lemon::NullMap "NullMap")
+    ///is needed for this phase.
     ///\pre The starting flow must be 
     ///- a constant zero flow if \c fp is \c ZERO_FLOW, 
     ///- an arbitary flow if \c fp is \c GEN_FLOW, 
@@ -232,6 +234,8 @@
     ///minCut returns a minimum cut.
     ///\warning \ref minMinCut() and \ref maxMinCut() do not
     ///give minimum value cuts unless calling \ref phase2().
+    ///\warning A real flow map (i.e. not \ref lemon::NullMap "NullMap")
+    ///is needed for this phase.
     void phase1()
     {
       int heur0=int(H0*_node_num);  //time while running 'bound decrease'