diff --git a/src/math/lp/nla_basics_lemmas.cpp b/src/math/lp/nla_basics_lemmas.cpp
index bcfcdfce9..5859b50fe 100644
--- a/src/math/lp/nla_basics_lemmas.cpp
+++ b/src/math/lp/nla_basics_lemmas.cpp
@@ -91,7 +91,7 @@ void basics::basic_sign_lemma_model_based_one_mon(const monic& m, int product_si
         TRACE("nla_solver_bl", tout << "zero product sign: " << pp_mon(_(), m)<< "\n"; );
         generate_zero_lemmas(m);
     } else {
-        new_lemma lemma(c());
+        new_lemma lemma(c(), __FUNCTION__);
         for(lpvar j: m.vars()) {
             negate_strict_sign(j);
         }
@@ -157,7 +157,7 @@ bool basics::basic_sign_lemma(bool derived) {
 // the value of the i-th monic has to be equal to the value of the k-th monic modulo sign
 // but it is not the case in the model
 void basics::generate_sign_lemma(const monic& m, const monic& n, const rational& sign) {
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "sign lemma");
     TRACE("nla_solver",
           tout << "m = " << pp_mon_with_vars(_(), m);
           tout << "n = " << pp_mon_with_vars(_(), n);
@@ -184,14 +184,14 @@ lpvar basics::find_best_zero(const monic& m, unsigned_vector & fixed_zeros) cons
     return zero_j;    
 }
 void basics::add_trival_zero_lemma(lpvar zero_j, const monic& m) {
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "x = 0 or x != 0");
     c().mk_ineq(zero_j, llc::NE);
     c().mk_ineq(m.var(), llc::EQ);
 }
 void basics::generate_strict_case_zero_lemma(const monic& m, unsigned zero_j, int sign_of_zj) {
     TRACE("nla_solver_bl", tout << "sign_of_zj = " << sign_of_zj << "\n";);
     // we know all the signs
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "strict case 0");
     c().mk_ineq(zero_j, (sign_of_zj == 1? llc::GT : llc::LT));
     for (unsigned j : m.vars()){
         if (j != zero_j) {
@@ -201,7 +201,7 @@ void basics::generate_strict_case_zero_lemma(const monic& m, unsigned zero_j, in
     negate_strict_sign(m.var());
 }
 void basics::add_fixed_zero_lemma(const monic& m, lpvar j) {
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "fixed zero");
     c().explain_fixed_var(j);
     c().mk_ineq(m.var(), llc::EQ);
 }
@@ -229,7 +229,7 @@ bool basics::basic_lemma_for_mon_zero(const monic& rm, const factorization& f) {
     return true;
 #if 0
     TRACE("nla_solver", c().trace_print_monic_and_factorization(rm, f, tout););
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "xy = 0 -> x = 0 or y = 0");
     c().explain_fixed_var(var(rm));
     std::unordered_set<lpvar> processed;
     for (auto j : f) {
@@ -247,7 +247,7 @@ bool basics::basic_lemma(bool derived) {
     if (derived) 
         return false;
     const auto& mon_inds_to_ref = c().m_to_refine;
-    TRACE("nla_solver", tout << "mon_inds_to_ref = "; print_vector(mon_inds_to_ref, tout););
+    TRACE("nla_solver", tout << "mon_inds_to_ref = "; print_vector(mon_inds_to_ref, tout) << "\n";);
     unsigned start = c().random();
     unsigned sz = mon_inds_to_ref.size();
     for (unsigned j = 0; j < sz; ++j) {
@@ -309,7 +309,7 @@ bool basics::basic_lemma_for_mon_non_zero_derived(const monic& rm, const factori
     if (zero_j == null_lpvar) {
         return false;
     } 
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "x = 0 or y = 0 -> xy = 0");
     c().explain_fixed_var(zero_j);
     c().explain_var_separated_from_zero(var(rm));
     explain(rm);
@@ -357,7 +357,7 @@ bool basics::basic_lemma_for_mon_neutral_monic_to_factor_derived(const monic& rm
         return false;
     } 
 
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "|xa| = |x| & x != 0 -> |a| = 1");
     // mon_var = 0
     if (mon_var_is_sep_from_zero)
          c().explain_var_separated_from_zero(mon_var);
@@ -418,7 +418,7 @@ bool basics::proportion_lemma_derived(const monic& rm, const factorization& fact
 }
 // if there are no zero factors then |m| >= |m[factor_index]|
 void basics::generate_pl_on_mon(const monic& m, unsigned factor_index) {
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "generate_pl_on_mon");
     unsigned mon_var = m.var();
     rational mv = val(mon_var);
     rational sm = rational(nla::rat_sign(mv));
@@ -448,7 +448,7 @@ void basics::generate_pl(const monic& m, const factorization& fc, int factor_ind
         generate_pl_on_mon(m, factor_index);
         return;
     }
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "generate_pl");
     int fi = 0;
     rational mv = var_val(m);
     rational sm = rational(nla::rat_sign(mv));
@@ -496,7 +496,7 @@ bool basics::factorization_has_real(const factorization& f) const {
 void basics::basic_lemma_for_mon_zero_model_based(const monic& rm, const factorization& f) {        
     TRACE("nla_solver",  c().trace_print_monic_and_factorization(rm, f, tout););
     SASSERT(var_val(rm).is_zero()&& ! c().rm_check(rm));
-    new_lemma lemma(c());
+    new_lemma lemma(c(), "xy = 0 -> x = 0 or y = 0");
     if (!is_separated_from_zero(f)) {
         c().mk_ineq(var(rm), llc::NE);        
         for (auto j : f) {
@@ -552,8 +552,10 @@ bool basics::basic_lemma_for_mon_neutral_monic_to_factor_model_based_fm(const mo
     if (jl == null_lpvar)
         return false;
     lpvar not_one_j = null_lpvar;
+    unsigned num_occs = 0;
     for (auto j : m.vars() ) {
         if (j == jl) {
+            ++num_occs;
             continue;
         }
         if (abs(val(j)) != rational(1)) {
@@ -562,11 +564,14 @@ bool basics::basic_lemma_for_mon_neutral_monic_to_factor_model_based_fm(const mo
         }
     }
 
+    if (num_occs > 1)
+        return false;
+    
     if (not_one_j == null_lpvar) {
         return false;
     } 
 
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     // mon_var = 0
     c().mk_ineq(mon_var, llc::EQ);
         
@@ -614,7 +619,7 @@ bool basics::basic_lemma_for_mon_neutral_from_factors_to_monic_model_based_fm(co
         }
     }
        
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     for (auto j : m.vars()){
         if (not_one == j) continue;
         c().mk_ineq(j, llc::NE, val(j));   
@@ -666,7 +671,7 @@ bool basics::basic_lemma_for_mon_neutral_monic_to_factor_model_based(const monic
         return false;
     } 
 
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     // mon_var = 0
     c().mk_ineq(mon_var, llc::EQ);
         
@@ -748,7 +753,7 @@ bool basics::basic_lemma_for_mon_neutral_from_factors_to_monic_model_based(const
 
     TRACE("nla_solver_bl", tout << "not_one = " << not_one << "\n";);
         
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
 
     for (auto j : f) {
         lpvar var_j = var(j);
@@ -780,7 +785,7 @@ void basics::basic_lemma_for_mon_non_zero_model_based_mf(const factorization& f)
     }
 
     if (zero_j == null_lpvar) { return; } 
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     c().mk_ineq(zero_j, llc::NE);
     c().mk_ineq(f.mon().var(), llc::EQ);
 }
diff --git a/src/math/lp/nla_core.cpp b/src/math/lp/nla_core.cpp
index 0b663f9be..dcb2dcaa3 100644
--- a/src/math/lp/nla_core.cpp
+++ b/src/math/lp/nla_core.cpp
@@ -1233,13 +1233,13 @@ rational core::val(const factorization& f) const {
     return r;
 }
 
-new_lemma::new_lemma(core& c):c(c) {
+new_lemma::new_lemma(core& c, char const* name):name(name), c(c) {
     c.m_lemma_vec->push_back(lemma());
 }
 
 new_lemma::~new_lemma() {
     // code for checking lemma can be added here
-    TRACE("nla_solver", tout << *this; );
+    TRACE("nla_solver", tout << name << "\n" << *this; );
 }
 
 lemma& new_lemma::operator()() {
@@ -1247,7 +1247,29 @@ lemma& new_lemma::operator()() {
 }
 
 std::ostream& new_lemma::display(std::ostream & out) const {
-    return c.print_specific_lemma(c.current_lemma(), out);
+    auto const& lemma = c.current_lemma();
+
+    for (auto &p : lemma.expl()) {
+        out << "(" << p.second << ") ";
+        c.m_lar_solver.constraints().display(out, [this](lpvar j) { return c.var_str(j);}, p.second);
+    }
+    out << " ==> ";
+    if (lemma.ineqs().empty()) {
+        out << "false";
+    }
+    else {
+        bool first = true;
+        for (auto & in : lemma.ineqs()) {
+            if (first) first = false; else out << " or ";
+            c.print_ineq(in, out);
+        }
+    }
+    out << "\n";
+    for (lpvar j : c.collect_vars(lemma)) {
+        c.print_var(j, out);
+    }
+
+    return out;
 }
     
 void core::negate_relation(unsigned j, const rational& a) {
@@ -1674,7 +1696,7 @@ bool core::check_pdd_eq(const dd::solver::equation* e) {
         return false;
     eval.get_interval<dd::w_dep::with_deps>(e->poly(), i_wd);  
     std::function<void (const lp::explanation&)> f = [this](const lp::explanation& e) {
-        new_lemma lemma(*this);
+        new_lemma lemma(*this, "pdd");
         current_expl().add(e);
     };
     if (di.check_interval_for_conflict_on_zero(i_wd, e->dep(), f)) {
diff --git a/src/math/lp/nla_core.h b/src/math/lp/nla_core.h
index a7c0ec952..e971a2b78 100644
--- a/src/math/lp/nla_core.h
+++ b/src/math/lp/nla_core.h
@@ -82,9 +82,10 @@ class core;
 // correctness of the lemma can be checked at this point.
 //
 class new_lemma {
+    char const* name;
     core& c;
 public:
-    new_lemma(core& c);
+    new_lemma(core& c, char const* name);
     ~new_lemma();
     lemma& operator()();
     std::ostream& display(std::ostream& out) const;
diff --git a/src/math/lp/nla_intervals.cpp b/src/math/lp/nla_intervals.cpp
index 751f2b342..ae6d64afa 100644
--- a/src/math/lp/nla_intervals.cpp
+++ b/src/math/lp/nla_intervals.cpp
@@ -84,7 +84,7 @@ bool intervals::check_nex(const nex* n, u_dependency* initial_deps) {
     m_core->lp_settings().stats().m_cross_nested_forms++;
     scoped_dep_interval i(get_dep_intervals());
     std::function<void (const lp::explanation&)> f = [this](const lp::explanation& e) {
-        new_lemma lemma(*m_core);
+        new_lemma lemma(*m_core, "check_nex");
         m_core->current_expl().add(e);
     };
     if (!interval_of_expr<e_with_deps::without_deps>(n, 1, i, f)) {
diff --git a/src/math/lp/nla_monotone_lemmas.cpp b/src/math/lp/nla_monotone_lemmas.cpp
index 378afb8cb..b88586a19 100644
--- a/src/math/lp/nla_monotone_lemmas.cpp
+++ b/src/math/lp/nla_monotone_lemmas.cpp
@@ -50,7 +50,7 @@ void monotone::monotonicity_lemma(monic const& m) {
 void monotone::monotonicity_lemma_gt(const monic& m, const rational& prod_val) {
     TRACE("nla_solver", tout << "prod_val = " << prod_val << "\n";
           tout << "m = "; c().print_monic_with_vars(m, tout););
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     for (lpvar j : m.vars()) {
         c().add_abs_bound(j, llc::GT);
     }
@@ -66,7 +66,7 @@ void monotone::monotonicity_lemma_gt(const monic& m, const rational& prod_val) {
     \/_i |m[i]| < |val(m[i])} or |m| >= |product_i val(m[i])|
 */
 void monotone::monotonicity_lemma_lt(const monic& m, const rational& prod_val) {
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     for (lpvar j : m.vars()) {
         c().add_abs_bound(j, llc::LT);
     }
diff --git a/src/math/lp/nla_order_lemmas.cpp b/src/math/lp/nla_order_lemmas.cpp
index 38aa8cf5e..0f65f4793 100644
--- a/src/math/lp/nla_order_lemmas.cpp
+++ b/src/math/lp/nla_order_lemmas.cpp
@@ -92,7 +92,7 @@ void order::order_lemma_on_binomial(const monic& ac) {
 void order::order_lemma_on_binomial_sign(const monic& xy, lpvar x, lpvar y, int sign) {
     SASSERT(!_().mon_has_zero(xy.vars()));
     int sy = rat_sign(val(y));
-    new_lemma lemma(c());
+    new_lemma lemma(c(), __FUNCTION__);
     mk_ineq(y,                     sy == 1      ? llc::LE : llc::GE); // negate sy
     mk_ineq(x,                     sy*sign == 1 ? llc::GT : llc::LT , val(x)); 
     mk_ineq(xy.var(), - val(x), y, sign == 1    ? llc::LE : llc::GE);
@@ -174,7 +174,7 @@ void order::generate_mon_ol(const monic& ac,
     SASSERT(ab_cmp != llc::LT || (var_val(ac) >= var_val(bd) && val(a)*c_sign < val(b)*d_sign));
     SASSERT(ab_cmp != llc::GT || (var_val(ac) <= var_val(bd) && val(a)*c_sign > val(b)*d_sign));
     
-    new_lemma lemma(_());
+    new_lemma lemma(_(), __FUNCTION__);
     mk_ineq(c_sign, c, llc::LE);
     explain(c); // this explains c == +- d
     mk_ineq(c_sign, a, -d_sign * b.rat_sign(), b.var(), negate(ab_cmp));
@@ -223,7 +223,7 @@ void order::order_lemma_on_factorization(const monic& m, const factorization& ab
     if (mv != fv) {
         bool gt = mv > fv;
         for (unsigned j = 0, k = 1; j < 2; j++, k--) {
-            new_lemma lemma(_());
+            new_lemma lemma(_(), __FUNCTION__);
             order_lemma_on_ab(lemma, m, rsign, var(ab[k]), var(ab[j]), gt);
             explain(ab); 
             explain(m);
@@ -261,7 +261,7 @@ void order::generate_ol_eq(const monic& ac,
                         const monic& bc,
                         const factor& b)                        {
     
-    new_lemma lemma(_());
+    new_lemma lemma(_(), __FUNCTION__);
 #if 0
     IF_VERBOSE(0, verbose_stream() << var_val(ac) << "(" << mul_val(ac) << "): " << ac 
                << " " << ab_cmp << " " << var_val(bc) << "(" << mul_val(bc) << "): " << bc << "\n"
@@ -287,7 +287,7 @@ void order::generate_ol(const monic& ac,
                         const monic& bc,
                         const factor& b)                        {
     
-    new_lemma lemma(_());
+    new_lemma lemma(_(), __FUNCTION__);
 #if 0
     IF_VERBOSE(0, verbose_stream() << var_val(ac) << "(" << mul_val(ac) << "): " << ac 
                << " " << ab_cmp << " " << var_val(bc) << "(" << mul_val(bc) << "): " << bc << "\n"
diff --git a/src/math/lp/nla_tangent_lemmas.cpp b/src/math/lp/nla_tangent_lemmas.cpp
index 3d515d7af..a32415cf9 100644
--- a/src/math/lp/nla_tangent_lemmas.cpp
+++ b/src/math/lp/nla_tangent_lemmas.cpp
@@ -74,7 +74,7 @@ struct imp {
 
 
     void generate_tang_plane(const point & pl) {
-        new_lemma lemma(c());
+        new_lemma lemma(c(), "generate tangent plane");
         c().negate_relation(m_jx, m_x.rat_sign()*pl.x);
         c().negate_relation(m_jy, m_y.rat_sign()*pl.y);
 #if Z3DEBUG
@@ -95,13 +95,13 @@ struct imp {
     
     void generate_two_tang_lines() {
         {
-            new_lemma lemma(c());
+            new_lemma lemma(c(), "two tangent planes 1");
             // Should be  v = val(m_x)*val(m_y), and val(factor) = factor.rat_sign()*var(factor.var())
             c().mk_ineq(m_jx, llc::NE, c().val(m_jx));
             c().mk_ineq(m_j,  - m_y.rat_sign() * m_xy.x,  m_jy, llc::EQ);
         }
         {
-            new_lemma lemma(c());
+            new_lemma lemma(c(), "two tangent planes 2");
             c().mk_ineq(m_jy, llc::NE, c().val(m_jy));
             c().mk_ineq(m_j, - m_x.rat_sign() * m_xy.y, m_jx, llc::EQ);
         }