diff --git a/include/fintamath/expressions/Expression.hpp b/include/fintamath/expressions/Expression.hpp
index e5d3419e7..c5184a1b9 100644
--- a/include/fintamath/expressions/Expression.hpp
+++ b/include/fintamath/expressions/Expression.hpp
@@ -136,8 +136,12 @@ class Expression : public IExpressionCRTP<Expression> {
 
   static void preciseRec(ArgumentPtr &arg, uint8_t precision);
 
+  friend std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsPtrVector &args);
+
   friend std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsRefVector &args);
 
+  friend std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsPtrVector &args);
+
   friend std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsPtrVector &args);
 
   friend ArgumentPtr parseExpr(const std::string &str);
diff --git a/include/fintamath/expressions/ExpressionUtils.hpp b/include/fintamath/expressions/ExpressionUtils.hpp
index 271659765..efd802772 100644
--- a/include/fintamath/expressions/ExpressionUtils.hpp
+++ b/include/fintamath/expressions/ExpressionUtils.hpp
@@ -28,4 +28,6 @@ bool hasVariable(const std::shared_ptr<const IExpression> &expr, const Variable
 
 std::vector<std::string> argumentVectorToStringVector(const ArgumentsPtrVector &args);
 
+ArgumentsPtrVector argumentRefVectorToArgumentPtrVector(const ArgumentsRefVector &args);
+
 }
diff --git a/include/fintamath/functions/FunctionUtils.hpp b/include/fintamath/functions/FunctionUtils.hpp
index 1fa99cb9d..04647682b 100644
--- a/include/fintamath/functions/FunctionUtils.hpp
+++ b/include/fintamath/functions/FunctionUtils.hpp
@@ -13,10 +13,14 @@ class IFunction;
 
 extern bool isExpression(const IMathObject &arg);
 
+extern std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsPtrVector &args);
+
 extern std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsRefVector &args);
 
 extern std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsPtrVector &args);
 
+extern std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsRefVector &args);
+
 template <typename T, typename = std::enable_if_t<std::is_convertible_v<T, ArgumentPtr>>>
 ArgumentPtr toArgumentPtr(T &arg) {
   if constexpr (std::is_copy_constructible_v<T>) {
diff --git a/include/fintamath/functions/IFunctionCRTP.hpp b/include/fintamath/functions/IFunctionCRTP.hpp
index 74731972a..89e339515 100644
--- a/include/fintamath/functions/IFunctionCRTP.hpp
+++ b/include/fintamath/functions/IFunctionCRTP.hpp
@@ -56,7 +56,11 @@ class IFunctionCRTP_ : public IFunction {
     validateArgsSize(argsVect);
 
     if (doArgsMatch(argsVect)) {
-      return call(argsVect);
+      if (auto res = call(argsVect)) {
+        return res;
+      }
+
+      return makeExpr(*this, argsVect);
     }
 
     return makeExprChecked(*this, argsVect);
diff --git a/src/fintamath/expressions/Expression.cpp b/src/fintamath/expressions/Expression.cpp
index e820e9c6c..f9f95c33a 100644
--- a/src/fintamath/expressions/Expression.cpp
+++ b/src/fintamath/expressions/Expression.cpp
@@ -497,17 +497,15 @@ void Expression::preciseRec(ArgumentPtr &arg, uint8_t precision) {
   }
 }
 
-std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsRefVector &args) {
-  ArgumentsPtrVector argsPtrVect;
-
-  for (const auto &arg : args) {
-    argsPtrVect.emplace_back(arg.get().clone());
-  }
-
-  Expression res(makeExpr(func, argsPtrVect));
+std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsPtrVector &args) {
+  Expression res(makeExpr(func, args));
   return res.getChildren().front()->clone();
 }
 
+std::unique_ptr<IMathObject> makeExprChecked(const IFunction &func, const ArgumentsRefVector &args) {
+  return makeExprChecked(func, argumentRefVectorToArgumentPtrVector(args));
+}
+
 std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsPtrVector &args) {
   if (auto expr = Parser::parse(Expression::getExpressionMakers(), func.toString(), args)) {
     return expr;
@@ -516,6 +514,10 @@ std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsPtrV
   return std::make_unique<FunctionExpression>(func, args);
 }
 
+std::unique_ptr<IMathObject> makeExpr(const IFunction &func, const ArgumentsRefVector &args) {
+  return makeExpr(func, argumentRefVectorToArgumentPtrVector(args));
+}
+
 void Expression::setChildren(const ArgumentsPtrVector &childVect) {
   if (childVect.size() != 1) {
     throw InvalidInputFunctionException("", argumentVectorToStringVector(childVect));
diff --git a/src/fintamath/expressions/ExpressionUtils.cpp b/src/fintamath/expressions/ExpressionUtils.cpp
index db669832c..a81daab7f 100644
--- a/src/fintamath/expressions/ExpressionUtils.cpp
+++ b/src/fintamath/expressions/ExpressionUtils.cpp
@@ -141,8 +141,18 @@ std::vector<std::string> argumentVectorToStringVector(const ArgumentsPtrVector &
   return argStrings;
 }
 
+ArgumentsPtrVector argumentRefVectorToArgumentPtrVector(const ArgumentsRefVector &args) {
+  ArgumentsPtrVector argsPtrVect;
+
+  for (const auto &arg : args) {
+    argsPtrVect.emplace_back(arg.get().clone());
+  }
+
+  return argsPtrVect;
+}
+
 bool isExpression(const IMathObject &arg) {
   return is<IExpression>(arg);
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/fintamath/functions/other/Factorial.cpp b/src/fintamath/functions/other/Factorial.cpp
index 579eb5baf..009afe8b2 100644
--- a/src/fintamath/functions/other/Factorial.cpp
+++ b/src/fintamath/functions/other/Factorial.cpp
@@ -38,7 +38,7 @@ std::unique_ptr<IMathObject> Factorial::multiFactorialSimpl(const INumber &lhs,
 std::unique_ptr<IMathObject> Factorial::factorialSimpl(const Integer &rhs, size_t order) {
   if (rhs < 0) {
     if (order != 1) {
-      return makeExpr(Factorial(order), rhs);
+      return {};
     }
 
     return ComplexInf().clone();
@@ -53,7 +53,7 @@ std::unique_ptr<IMathObject> Factorial::factorialSimpl(const Rational &rhs, size
   }
 
   if (order != 1) {
-    return makeExpr(Factorial(order), rhs);
+    return {};
   }
 
   return factorialSimpl(Real(rhs), order);
@@ -61,14 +61,14 @@ std::unique_ptr<IMathObject> Factorial::factorialSimpl(const Rational &rhs, size
 
 std::unique_ptr<IMathObject> Factorial::factorialSimpl(const Real &rhs, size_t order) {
   if (order != 1) {
-    return makeExpr(Factorial(order), rhs);
+    return {};
   }
 
   try {
     return tgamma(rhs + 1).toMinimalObject();
   }
   catch (const UndefinedException &) {
-    return makeExpr(Factorial(order), rhs);
+    return {};
   }
 }
 
diff --git a/src/fintamath/functions/powers/Pow.cpp b/src/fintamath/functions/powers/Pow.cpp
index c3e20ce79..0a8587322 100644
--- a/src/fintamath/functions/powers/Pow.cpp
+++ b/src/fintamath/functions/powers/Pow.cpp
@@ -79,7 +79,7 @@ std::unique_ptr<IMathObject> Pow::powSimpl(const Rational &lhs, const Rational &
 
   if (lhs < Integer(0)) {
     // TODO: complex numbers
-    return makeExpr(Pow(), lhs, rhs);
+    return {};
   }
 
   if (lhsDenominator == 1) {
@@ -94,7 +94,7 @@ std::unique_ptr<IMathObject> Pow::powSimpl(const Real &lhs, const Real &rhs) {
     return pow(lhs, rhs).toMinimalObject();
   }
   catch (const UndefinedException &) {
-    return makeExpr(Pow(), lhs, rhs);
+    return {};
   }
 }
 
diff --git a/src/fintamath/functions/powers/Root.cpp b/src/fintamath/functions/powers/Root.cpp
index dbae8bbf7..58c145a97 100644
--- a/src/fintamath/functions/powers/Root.cpp
+++ b/src/fintamath/functions/powers/Root.cpp
@@ -26,7 +26,7 @@ std::unique_ptr<IMathObject> Root::call(const ArgumentsRefVector &argsVect) cons
     if (rhsInt > Integer(1)) {
       if (lhs < Integer(0)) {
         // TODO: complex numbers
-        return makeExpr(Root(), lhs, rhs);
+        return {};
       }
 
       return multiRootSimpl(lhs, rhsInt);
diff --git a/tests/src/expressions/ExpressionUtilsTests.cpp b/tests/src/expressions/ExpressionUtilsTests.cpp
index 79d6c5193..3379a060c 100644
--- a/tests/src/expressions/ExpressionUtilsTests.cpp
+++ b/tests/src/expressions/ExpressionUtilsTests.cpp
@@ -43,6 +43,10 @@ TEST(ExpressionUtilsTests, argumentVectorToStringVectorTest) {
   // TODO: implement
 }
 
+TEST(ExpressionUtilsTests, argumentRefVectorToArgumentPtrVector) {
+  // TODO: implement
+}
+
 TEST(ExpressionUtilsTests, hasVariableTest) {
   auto expr = std::make_shared<Expression>("cos(sin(a))");
   EXPECT_TRUE(hasVariable(expr, Variable("a")));
diff --git a/tests/src/functions/FunctionUtilsTests.cpp b/tests/src/functions/FunctionUtilsTests.cpp
index 0fbeeba14..f5571f6bd 100644
--- a/tests/src/functions/FunctionUtilsTests.cpp
+++ b/tests/src/functions/FunctionUtilsTests.cpp
@@ -18,7 +18,25 @@
 
 using namespace fintamath;
 
-TEST(FunctionUtilsTests, makeExpressionCheckedTest) {
+TEST(FunctionUtilsTests, makeExpressionCheckedPtrsTest) {
+  ArgumentPtr one = std::make_unique<Integer>(1);
+  ArgumentPtr two = std::make_unique<Integer>(2);
+  auto expr1 = makeExprChecked(Add(), {one, two});
+  EXPECT_EQ(expr1->toString(), "3");
+  EXPECT_TRUE(is<INumber>(expr1));
+
+  ArgumentPtr var = std::make_unique<Variable>("a");
+  ArgumentPtr expr2 = makeExprChecked(Cos(), {var});
+  EXPECT_EQ(expr2->toString(), "cos(a)");
+  EXPECT_TRUE(is<IExpression>(expr2));
+
+  EXPECT_THROW(makeExprChecked(Mul(), ArgumentsPtrVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Mul(), ArgumentsPtrVector{})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Pow(), ArgumentsPtrVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Pow(), ArgumentsPtrVector{})->toString(), InvalidInputException);
+}
+
+TEST(FunctionUtilsTests, makeExpressionCheckedRefsTest) {
   Integer one = 1;
   Integer two = 2;
   auto expr1 = makeExprChecked(Add(), {one, two});
@@ -29,24 +47,47 @@ TEST(FunctionUtilsTests, makeExpressionCheckedTest) {
   auto expr2 = makeExprChecked(Cos(), {var});
   EXPECT_EQ(expr2->toString(), "cos(a)");
   EXPECT_TRUE(is<IExpression>(expr2));
+
+  EXPECT_THROW(makeExprChecked(Mul(), ArgumentsRefVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Mul(), ArgumentsRefVector{})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Pow(), ArgumentsRefVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExprChecked(Pow(), ArgumentsRefVector{})->toString(), InvalidInputException);
 }
 
-TEST(FunctionUtilsTests, makeExpressionTest) {
-  auto expr1 = makeExpr(Add(), {std::make_shared<Integer>(1), std::make_shared<Integer>(2)});
+TEST(FunctionUtilsTests, makeExpressionPtrsTest) {
+  ArgumentPtr one = std::make_unique<Integer>(1);
+  ArgumentPtr two = std::make_unique<Integer>(2);
+  auto expr1 = makeExpr(Add(), {one, two});
   EXPECT_EQ(expr1->toString(), "1 + 2");
-  EXPECT_TRUE(is<IExpression>(expr1));
-  EXPECT_FALSE(is<Expression>(expr1));
+  EXPECT_FALSE(is<INumber>(expr1));
 
-  auto var = std::make_shared<Variable>("a");
+  ArgumentPtr var = std::make_unique<Variable>("a");
+  ArgumentPtr expr2 = makeExpr(Cos(), {var});
+  EXPECT_EQ(expr2->toString(), "cos(a)");
+  EXPECT_TRUE(is<IExpression>(expr2));
+
+  EXPECT_THROW(makeExpr(Mul(), ArgumentsPtrVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Mul(), ArgumentsPtrVector{})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Pow(), ArgumentsPtrVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Pow(), ArgumentsPtrVector{})->toString(), InvalidInputException);
+}
+
+TEST(FunctionUtilsTests, makeExpressionRefsTest) {
+  Integer one = 1;
+  Integer two = 2;
+  auto expr1 = makeExpr(Add(), {one, two});
+  EXPECT_EQ(expr1->toString(), "1 + 2");
+  EXPECT_FALSE(is<INumber>(expr1));
+
+  Variable var("a");
   auto expr2 = makeExpr(Cos(), {var});
   EXPECT_EQ(expr2->toString(), "cos(a)");
   EXPECT_TRUE(is<IExpression>(expr2));
-  EXPECT_FALSE(is<Expression>(expr2));
 
-  EXPECT_THROW(makeExpr(Mul(), {var})->toString(), InvalidInputException);
-  EXPECT_THROW(makeExpr(Mul(), {})->toString(), InvalidInputException);
-  EXPECT_THROW(makeExpr(Pow(), {var})->toString(), InvalidInputException);
-  EXPECT_THROW(makeExpr(Pow(), {})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Mul(), ArgumentsRefVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Mul(), ArgumentsRefVector{})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Pow(), ArgumentsRefVector{var})->toString(), InvalidInputException);
+  EXPECT_THROW(makeExpr(Pow(), ArgumentsRefVector{})->toString(), InvalidInputException);
 }
 
 TEST(FunctionUtilsTests, makeExpressionCheckedAnyArgsTest) {
diff --git a/tests/src/functions/powers/PowTests.cpp b/tests/src/functions/powers/PowTests.cpp
index dbe4725af..8e42f2816 100644
--- a/tests/src/functions/powers/PowTests.cpp
+++ b/tests/src/functions/powers/PowTests.cpp
@@ -75,7 +75,7 @@ TEST(PowTests, callTest) {
   EXPECT_EQ(f(Real("2.2"), Real("0.5"))->toString(),
             "1.48323969741913258974227948816014261219598086381950031974652465286876603686277");
 
-  EXPECT_EQ(f(Rational(-10), Rational("-1.5"))->toString(), "(-1/10)^(3/2)");
+  EXPECT_EQ(f(Rational(-10), Rational("-1.5"))->toString(), "(-10)^(-3/2)");
 
   EXPECT_EQ(f(Integer(0), Integer(-1))->toString(), "ComplexInf");
   EXPECT_EQ(f(Integer(0), Integer(-10))->toString(), "ComplexInf");
diff --git a/tests/src/functions/powers/RootTests.cpp b/tests/src/functions/powers/RootTests.cpp
index 279058217..ce9641ffb 100644
--- a/tests/src/functions/powers/RootTests.cpp
+++ b/tests/src/functions/powers/RootTests.cpp
@@ -94,7 +94,7 @@ TEST(RootTests, callTest) {
 
   EXPECT_EQ(f(Integer(-10), Integer(2))->toString(), "sqrt(-10)");
   EXPECT_EQ(f(Rational(-9289, 10), Rational(2, 3))->toString(), "(-9289/10)^(3/2)");
-  EXPECT_EQ(f(Real(-9289), Rational(2, 3))->toString(), "(-9289.0)^1.5");
+  EXPECT_EQ(f(Real(-9289), Rational(2, 3))->toString(), "(-9289.0)^(3/2)");
 
   EXPECT_THROW(f(), InvalidInputFunctionException);
   EXPECT_THROW(f(Integer(1), Integer(1), Integer(1)), InvalidInputFunctionException);