diff --git a/src/util/lp/emonomials.cpp b/src/util/lp/emonomials.cpp
index 512172702..8132d7ed4 100644
--- a/src/util/lp/emonomials.cpp
+++ b/src/util/lp/emonomials.cpp
@@ -150,6 +150,7 @@ monomial const* emonomials::find_canonical(svector<lpvar> const& vars) const {
 
 void emonomials::remove_cg(lpvar v) {
     cell* c = m_use_lists[v].m_head;
+    CTRACE("nla_solver", v == 14, tout << c << "\n";);
     if (c == nullptr) {
         return;
     }
@@ -159,6 +160,7 @@ void emonomials::remove_cg(lpvar v) {
         unsigned idx = c->m_index;
         c = c->m_next;
         monomial & m = m_monomials[idx];
+        CTRACE("nla_solver", v == 14, tout << m << "\n";);
         if (!is_visited(m)) {
             set_visited(m);
             remove_cg(idx, m);
@@ -172,6 +174,7 @@ void emonomials::remove_cg(unsigned idx, monomial& m) {
     unsigned next = sv.next();
     unsigned prev = sv.prev();
         
+
     lpvar u = m.var(), w;
     // equivalence class of u:
     if (m_cg_table.find(u, w) && w == u) {
@@ -198,6 +201,8 @@ void emonomials::remove_cg(unsigned idx, monomial& m) {
 */
 void emonomials::insert_cg(lpvar v) {
     cell* c = m_use_lists[v].m_head;
+    CTRACE("nla_solver", v == 14, tout << c << "\n";);
+
     if (c == nullptr) {
         return;
     }
@@ -208,6 +213,7 @@ void emonomials::insert_cg(lpvar v) {
         unsigned idx = c->m_index;
         c = c->m_next;
         monomial & m = m_monomials[idx];
+        CTRACE("nla_solver", v == 14, tout << m << "\n";);
         if (!is_visited(m)) {
             set_visited(m);
             insert_cg(idx, m);
@@ -344,7 +350,8 @@ void emonomials::merge_eh(signed_var r2, signed_var r1, signed_var v2, signed_va
 }
 
 void emonomials::after_merge_eh(signed_var r2, signed_var r1, signed_var v2, signed_var v1) {
-    if (!r2.sign() && m_ve.find(~r2) != m_ve.find(r1)) {
+    TRACE("nla_solver", tout << r2 << " <- " << r1 << "\n";);
+    if (!r1.sign()) {
         m_use_lists.reserve(std::max(r2.var(), r1.var()) + 1);
         rehash_cg(r1.var()); 
         merge_cells(m_use_lists[r2.var()], m_use_lists[r1.var()]);
@@ -352,34 +359,49 @@ void emonomials::after_merge_eh(signed_var r2, signed_var r1, signed_var v2, sig
 }
 
 void emonomials::unmerge_eh(signed_var r2, signed_var r1) {
-    if (!r2.sign() && m_ve.find(~r2) != m_ve.find(r1)) {
+    TRACE("nla_solver", tout << r2 << " -> " << r1 << "\n";);
+    if (!r1.sign()) {
         unmerge_cells(m_use_lists[r2.var()], m_use_lists[r1.var()]);            
         rehash_cg(r1.var());
     }        
 }
-
+ 
 std::ostream& emonomials::display(const core& cr, std::ostream& out) const {
     out << "monomials\n";
     unsigned idx = 0;
     for (auto const& m : m_monomials) {
-        out << (idx++) << ": " << pp_rmon(cr, m) << "\n";
-    }
-    out << "use lists\n";
-    idx = 0;
-    for (auto const& ht : m_use_lists) {
-        cell* c = ht.m_head;
-        if (c) {
-            out << "v" << idx << ": ";
-            do {
-                out << c->m_index << " ";
-                c = c->m_next;
-            }
-            while (c != ht.m_head);
-            out << "\n";
-        }
-        ++idx;
-    }
-    return out;
+        out << "m" << (idx++) << ": " << pp_rmon(cr, m) << "\n";
+    }    
+    return display_use(out);
 }
 
+std::ostream& emonomials::display(std::ostream& out) const {
+    out << "monomials\n";
+    unsigned idx = 0;
+    for (auto const& m : m_monomials) {
+        out << "m" << (idx++) << ": " << m << "\n";
+    }    
+    return display_use(out);
+}
+ 
+ std::ostream& emonomials::display_use(std::ostream& out) const {
+     out << "use lists\n";
+     unsigned idx = 0;
+     for (auto const& ht : m_use_lists) {
+         cell* c = ht.m_head;
+         if (c) {
+             out << idx << ": ";
+             do {
+                 out << "m" << c->m_index << " ";
+                 c = c->m_next;
+             }
+             while (c != ht.m_head);
+             out << "\n";
+         }
+         ++idx;
+     }
+     return out;
+ }
+
+
 }
diff --git a/src/util/lp/emonomials.h b/src/util/lp/emonomials.h
index b37c2ee51..37b5fe0d5 100644
--- a/src/util/lp/emonomials.h
+++ b/src/util/lp/emonomials.h
@@ -103,7 +103,7 @@ class emonomials : public var_eqs_merge_handler {
     cell* head(lpvar v) const;
     void set_visited(monomial& m) const;
     bool is_visited(monomial const& m) const;
-     
+    std::ostream& display_use(std::ostream& out) const; 
 public:
     /**
        \brief emonomials builds on top of var_eqs.
@@ -281,6 +281,7 @@ public:
        \brief display state of emonomials
     */
     std::ostream& display(const core&, std::ostream& out) const;
+    std::ostream& display(std::ostream& out) const;
 
     /**
        \brief
diff --git a/src/util/lp/monomial.h b/src/util/lp/monomial.h
index e0ebce7f5..9ce13de8a 100644
--- a/src/util/lp/monomial.h
+++ b/src/util/lp/monomial.h
@@ -70,6 +70,10 @@ public:
     }
 };
 
+ inline std::ostream& operator<<(std::ostream& out, monomial const& m) {
+     return out << m.var() << " := " << m.vars() << " r " << m.rsign() << " * " << m.rvars();
+ }
+
 
 typedef std::unordered_map<lpvar, rational> variable_map_type;
 template <typename T>
diff --git a/src/util/lp/nla_basics_lemmas.cpp b/src/util/lp/nla_basics_lemmas.cpp
index bb1df83cf..1a3d9fda8 100644
--- a/src/util/lp/nla_basics_lemmas.cpp
+++ b/src/util/lp/nla_basics_lemmas.cpp
@@ -123,6 +123,10 @@ bool basics::basic_sign_lemma_on_mon(lpvar v, std::unordered_set<unsigned> & exp
     }
     const monomial& m_v = c().m_emons[v];
     TRACE("nla_solver", tout << "m_v = " << pp_rmon(c(), m_v););
+    CTRACE("nla_solver", !c().m_emons.is_canonized(m_v),
+           c().m_emons.display(c(), tout);
+           c().m_evars.display(tout);
+           );
     SASSERT(c().m_emons.is_canonized(m_v));
 
     for (auto const& m : c().m_emons.enum_sign_equiv_monomials(v)) {
diff --git a/src/util/lp/var_eqs.cpp b/src/util/lp/var_eqs.cpp
index 5a71b1595..f215c0bbb 100644
--- a/src/util/lp/var_eqs.cpp
+++ b/src/util/lp/var_eqs.cpp
@@ -175,11 +175,14 @@ std::ostream& var_eqs::display(std::ostream& out) const {
     m_uf.display(out);
     unsigned idx = 0;
     for (auto const& edges : m_eqs) {
-        out << signed_var(idx, from_index_dummy()) << ": ";
-        for (auto const& jv : edges) {
-            out << jv.m_var << " ";
+        if (!edges.empty()) {
+            auto v = signed_var(idx, from_index_dummy());
+            out << v << " root: " << find(v) << " : ";
+            for (auto const& jv : edges) {
+                out << jv.m_var << " ";
+            }
+            out << "\n";
         }
-        out << "\n";
         ++idx;
     }
     return out;