diff --git a/src/math/lp/horner.cpp b/src/math/lp/horner.cpp
index 7d39b7611..3b24ab5cb 100644
--- a/src/math/lp/horner.cpp
+++ b/src/math/lp/horner.cpp
@@ -124,7 +124,7 @@ interv horner::interval_of_expr(const nex& e) {
     }
 }
 
-interv horner::interval_of_mul(const vector<nex>& es) {    
+interv horner::interval_of_mul(const std::vector<nex>& es) {    
     interv a = interval_of_expr(es[0]);
     //    std::cout << "a" << std::endl;
     TRACE("nla_cn_details", tout << "es[0]= "<< es[0] << std::endl << "a = "; m_intervals.display(tout, a); tout << "\n";);
@@ -150,7 +150,7 @@ interv horner::interval_of_mul(const vector<nex>& es) {
     return a;
 }
 
-interv horner::interval_of_sum(const vector<nex>& es) {
+interv horner::interval_of_sum(const std::vector<nex>& es) {
     interv a = interval_of_expr(es[0]);
     TRACE("nla_cn_details", tout << "es[0]= "  << es[0] << "\n"; m_intervals.display(tout, a) << "\n";);
     if (m_intervals.is_inf(a)) {
diff --git a/src/math/lp/horner.h b/src/math/lp/horner.h
index f4b2a30eb..0eb5c88a2 100644
--- a/src/math/lp/horner.h
+++ b/src/math/lp/horner.h
@@ -41,8 +41,8 @@ public:
     intervals::interval interval_of_expr(const nex& e);
     
     nex nexvar(lpvar j) const;
-    intervals::interval interval_of_sum(const vector<nex>&);
-    intervals::interval interval_of_mul(const vector<nex>&);
+    intervals::interval interval_of_sum(const std::vector<nex>&);
+    intervals::interval interval_of_mul(const std::vector<nex>&);
     void set_interval_for_scalar(intervals::interval&, const rational&);
     void set_var_interval(lpvar j, intervals::interval&);
     std::set<lpvar> get_vars_of_expr(const nex &) const;
diff --git a/src/math/lp/nla_expr.h b/src/math/lp/nla_expr.h
index c2582681e..83a800249 100644
--- a/src/math/lp/nla_expr.h
+++ b/src/math/lp/nla_expr.h
@@ -44,14 +44,40 @@ inline std::ostream & operator<<(std::ostream& out, expr_type t) {
     }
     return out;
 }
+
+
 // This class is needed in horner calculation with intervals
 template <typename T>
 class nla_expr {
+    
+class sorted_children {
+    std::vector<nla_expr> m_es;
+    // m_order will be sorted according to the non-decreasing order of m_es
+    svector<unsigned> m_order;
+public:
+    const std::vector<nla_expr>& es() const { return m_es; }
+    std::vector<nla_expr>& es() { return m_es; }
+    void push_back(const nla_expr& e) {
+        SASSERT(m_es.size() == m_order.size());
+        m_order.push_back(m_es.size());
+        m_es.push_back(e);
+    }
+    const svector<unsigned>& order() const { return m_order; }
+    const nla_expr& back() const { return m_es.back(); }
+    nla_expr& back() { return m_es.back(); }
+    const nla_expr* begin() const { return m_es.begin(); }
+    const nla_expr* end() const { return m_es.end(); }
+    unsigned size() const { return m_es.size(); }
+    void sort() {
+        std::sort(m_order.begin(), m_order.end(), [this](unsigned i, unsigned j) { return m_es[i] < m_es[j]; });
+    }
+};
+
     // todo: use union
     expr_type       m_type;
     lpvar           m_j;
     T             m_v; // for the scalar
-    vector<nla_expr> m_children;
+    sorted_children m_children;
 public:
     bool is_sum() const { return m_type == expr_type::SUM; }
     bool is_var() const { return m_type == expr_type::VAR; }
@@ -60,13 +86,16 @@ public:
     lpvar var() const { SASSERT(m_type == expr_type::VAR); return m_j; }
     expr_type type() const { return m_type; }
     expr_type& type() { return m_type; }
-    const vector<nla_expr>& children() const { return m_children; }
-    vector<nla_expr>& children() { return m_children; }
+    const std::vector<nla_expr>& children() const { return m_children.es(); }
+    std::vector<nla_expr>& children() { return m_children.es(); }
+    const sorted_children & s_children() const { return m_children; }
+    sorted_children & s_children() { return m_children; }
     const T& value() const { SASSERT(m_type == expr_type::SCALAR); return m_v; }
     std::string str() const { std::stringstream ss; ss << *this; return ss.str(); }
     std::ostream & print_sum(std::ostream& out) const {
         bool first = true;
-        for (const nla_expr& v : m_children) {
+        for (unsigned j : m_children.order()) {            
+            const nla_expr& v = m_children.es()[j];
             std::string s = v.str();
             if (first) {
                 first = false;
@@ -88,9 +117,18 @@ public:
         }
         return out;
     }
+    void sort () {
+        if (is_sum() || is_mul()) {
+            for (auto & e : m_children.es()) {
+                e.sort();
+            }
+            m_children.sort();
+        }            
+    }
     std::ostream & print_mul(std::ostream& out) const {
         bool first = true;
-        for (const nla_expr& v : m_children) {
+        for (unsigned j : m_children.order()) {            
+            const nla_expr& v = m_children.es()[j];
             std::string s = v.str();
             if (first) {
                 first = false;
@@ -221,13 +259,35 @@ public:
             }
         }
         return false;
-    }    
+    }
+    bool operator<(const nla_expr& e) const {
+        if (type() != (e.type()))
+            return (int)type() < (int)(e.type());
+
+        SASSERT(type() == (e.type()));
+
+        switch(m_type) {
+        case expr_type::SUM:
+        case expr_type::MUL:
+            return m_children.es() < e.m_children.es();
+        case expr_type::VAR:
+            return m_j < e.m_j;
+        case expr_type::SCALAR:
+            return m_v < e.m_v;
+        default:
+            SASSERT(false);
+            return false;
+        }
+
+        
+            
+    }
 };
 template <typename T> 
 nla_expr<T> operator+(const nla_expr<T>& a, const nla_expr<T>& b) {
     if (a.is_sum()) {
         nla_expr<T> r(expr_type::SUM);
-        r.children() = a.children();
+        r.s_children() = a.s_children();
         if (b.is_sum()) {
             for (auto& e: b.children())
                 r.add_child(e);
@@ -238,7 +298,7 @@ nla_expr<T> operator+(const nla_expr<T>& a, const nla_expr<T>& b) {
     }
     if (b.is_sum()) {
         nla_expr<T> r(expr_type::SUM);
-        r.children() = b.children();
+        r.s_children() = b.s_children();
         r.add_child(a);
         return r;
     }
@@ -249,7 +309,7 @@ template <typename T>
 nla_expr<T> operator*(const nla_expr<T>& a, const nla_expr<T>& b) {
     if (a.is_mul()) {
         nla_expr<T> r(expr_type::MUL);
-        r.children() = a.children();
+        r.s_children() = a.s_children();
         if (b.is_mul()) {
             for (auto& e: b.children())
                 r.add_child(e);
@@ -260,7 +320,7 @@ nla_expr<T> operator*(const nla_expr<T>& a, const nla_expr<T>& b) {
     }
     if (b.is_mul()) {
         nla_expr<T> r(expr_type::MUL);
-        r.children() = b.children();
+        r.s_children() = b.s_children();
         r.add_child(a);
         return r;
     }
diff --git a/src/smt/smt_context_pp.cpp b/src/smt/smt_context_pp.cpp
index 76dbfecba..05f4fc51d 100644
--- a/src/smt/smt_context_pp.cpp
+++ b/src/smt/smt_context_pp.cpp
@@ -491,7 +491,9 @@ namespace smt {
         std::stringstream strm;
         strm << "lemma_" << (++m_lemma_id) << ".smt2";
         std::ofstream out(strm.str());
-        TRACE("lemma", tout << strm.str() << "\n";);
+        TRACE("lemma", tout << strm.str() << "\n";
+              display_lemma_as_smt_problem(tout, num_antecedents, antecedents, num_eq_antecedents, eq_antecedents, consequent, logic);
+);
         display_lemma_as_smt_problem(out, num_antecedents, antecedents, num_eq_antecedents, eq_antecedents, consequent, logic);
         out.close();
 
diff --git a/src/test/lp/lp.cpp b/src/test/lp/lp.cpp
index 98c2af258..010e570a9 100644
--- a/src/test/lp/lp.cpp
+++ b/src/test/lp/lp.cpp
@@ -72,11 +72,32 @@ void test_cn() {
     enable_trace("nla_cn");
     // (a(a+(b+c)c+d)d + e(a(e+c)+d)
     nex a = nex::var(0), b = nex::var(1), c = nex::var(2), d = nex::var(3), e = nex::var(4);
-    nex t = a*a*d + a*b*c*d + a*c*c*d + a*d*d + e*a*e + e*a*c + e*d;
-    std::cout << "t = " << t << "\n";
-    TRACE("nla_cn", tout << "t=" << t << '\n';);
-    cross_nested cn(t, [](const nex& n) { std::cout << n << "\n"; } );
-    cn.run();
+    {
+        nex t = a*a*d + a*b*c*d + a*c*c*d + a*d*d + e*a*e + e*a*c + e*d;
+        std::cout << "t = " << t << "\n";
+        TRACE("nla_cn", tout << "t=" << t << '\n';);
+        cross_nested cn(t, [](const nex& n) {
+                               std::cout << n << "\n";
+                               auto nn = n;
+                               nn.sort();
+                               std::cout << "ordered version\n" << nn << "\n______________________\n";
+                           
+                           } );
+        cn.run();
+    }
+    {
+        nex t = a*b*d + a*b*c;
+        std::cout << "t = " << t << "\n";
+        TRACE("nla_cn", tout << "t=" << t << '\n';);
+        cross_nested cn(t, [](const nex& n) {
+                               std::cout << n << "\n";
+                               auto nn = n;
+                               nn.sort();
+                               std::cout << "ordered version\n" << nn << "\n______________________\n";
+                           
+                           } );
+        cn.run();
+    }
 }
 
 } // end of namespace nla