diff --git a/include/plasp/pddl/expressions/NAry.h b/include/plasp/pddl/expressions/NAry.h
index 3122ef0..1c749e3 100644
--- a/include/plasp/pddl/expressions/NAry.h
+++ b/include/plasp/pddl/expressions/NAry.h
@@ -178,7 +178,7 @@ inline ExpressionPointer NAry<Derived>::simplified()
 	}
 
 	// TODO: recognize tautologies
-	// TODO: introduce handle boolean values
+	// TODO: introduce/handle boolean values
 
 	return this;
 }
diff --git a/include/plasp/pddl/expressions/Quantified.h b/include/plasp/pddl/expressions/Quantified.h
index 15aa954..e7a1701 100644
--- a/include/plasp/pddl/expressions/Quantified.h
+++ b/include/plasp/pddl/expressions/Quantified.h
@@ -31,8 +31,12 @@ class Quantified: public ExpressionCRTP<Derived>
 		void setArgument(ExpressionPointer argument);
 		ExpressionPointer argument() const;
 
+		Variables &variables();
+		const Variables &variables() const;
+
 		ExpressionPointer reduced() override;
 		ExpressionPointer negationNormalized() override;
+		ExpressionPointer simplified() override;
 
 		void print(std::ostream &ostream) const override;
 
@@ -98,6 +102,22 @@ ExpressionPointer Quantified<Derived>::argument() const
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+template<class Derived>
+Variables &Quantified<Derived>::variables()
+{
+	return m_variables;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Derived>
+const Variables &Quantified<Derived>::variables() const
+{
+	return m_variables;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 template<class Derived>
 inline ExpressionPointer Quantified<Derived>::reduced()
 {
@@ -118,17 +138,43 @@ inline ExpressionPointer Quantified<Derived>::negationNormalized()
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+template<class Derived>
+inline ExpressionPointer Quantified<Derived>::simplified()
+{
+	m_argument = m_argument->simplified();
+
+	// Associate same-type children, such as (forall (?x) (forall (?y) (...)))
+	if (m_argument->expressionType() != Derived::ExpressionType)
+		return this;
+
+	auto &quantifiedExpression = dynamic_cast<Derived &>(*m_argument);
+
+	BOOST_ASSERT(!quantifiedExpression.arguments().empty());
+
+	// Unify variables
+	m_variables.insert(m_variables.end(), quantifiedExpression.variables().begin(), quantifiedExpression.variables().end());
+
+	// Move child expression up
+	m_argument = quantifiedExpression.argument();
+
+	// TODO: introduce/handle boolean values
+
+	return this;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 template<class Derived>
 inline void Quantified<Derived>::print(std::ostream &ostream) const
 {
-	ostream << "(" << Derived::Identifier << "(";
+	ostream << "(" << Derived::Identifier << " (";
 
 	for (size_t i = 0; i < m_variables.size(); i++)
 	{
 		if (i > 0)
 			ostream << " ";
 
-		ostream << m_variables[i]->name();
+		m_variables[i]->print(ostream);
 	}
 
 	ostream << ") ";
diff --git a/include/plasp/pddl/expressions/Variable.h b/include/plasp/pddl/expressions/Variable.h
index 654d0b4..7b6d890 100644
--- a/include/plasp/pddl/expressions/Variable.h
+++ b/include/plasp/pddl/expressions/Variable.h
@@ -27,6 +27,9 @@ class Variable: public ExpressionCRTP<Variable>
 			Variables &variables);
 
 	public:
+		Variable();
+		Variable(std::string name);
+
 		void setName(std::string name);
 		const std::string &name() const;
 
@@ -42,8 +45,6 @@ class Variable: public ExpressionCRTP<Variable>
 		static void parseDeclaration(Context &context, Variables &parameters);
 
 	private:
-		Variable();
-
 		bool m_isDirty;
 
 		std::string m_name;
diff --git a/src/plasp/pddl/expressions/Variable.cpp b/src/plasp/pddl/expressions/Variable.cpp
index 67a72a8..bc609d0 100644
--- a/src/plasp/pddl/expressions/Variable.cpp
+++ b/src/plasp/pddl/expressions/Variable.cpp
@@ -26,8 +26,15 @@ namespace expressions
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 Variable::Variable()
+:	m_isDirty{false}
+{
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+Variable::Variable(std::string name)
 :	m_isDirty{false},
-	m_type{nullptr}
+	m_name{name}
 {
 }
 
@@ -180,8 +187,13 @@ bool Variable::isDirty() const
 
 void Variable::print(std::ostream &ostream) const
 {
-	// TODO: implement correctly
-	ostream << "(<variable " << m_name << ">)";
+	ostream << "?" << m_name;
+
+	if (m_type)
+	{
+		ostream << " - ";
+		m_type->print(ostream);
+	}
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/tests/TestPDDLNormalization.cpp b/tests/TestPDDLNormalization.cpp
index 1747eac..a2d7274 100644
--- a/tests/TestPDDLNormalization.cpp
+++ b/tests/TestPDDLNormalization.cpp
@@ -2,9 +2,12 @@
 
 #include <plasp/pddl/expressions/And.h>
 #include <plasp/pddl/expressions/Dummy.h>
+#include <plasp/pddl/expressions/Exists.h>
+#include <plasp/pddl/expressions/ForAll.h>
 #include <plasp/pddl/expressions/Imply.h>
 #include <plasp/pddl/expressions/Not.h>
 #include <plasp/pddl/expressions/Or.h>
+#include <plasp/pddl/expressions/Variable.h>
 
 using namespace plasp::pddl;
 
@@ -155,3 +158,31 @@ TEST(PDDLNormalizationTests, DoubleNegationInner)
 
 	ASSERT_EQ(output.str(), "(or (not (a)) (not (b)) (not (c)))");
 }
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+TEST(PDDLNormalizationTests, SimplifyNestedForAll)
+{
+	auto v1 = expressions::VariablePointer(new expressions::Variable("x"));
+	auto v2 = expressions::VariablePointer(new expressions::Variable("y"));
+	auto v3 = expressions::VariablePointer(new expressions::Variable("z"));
+	auto v4 = expressions::VariablePointer(new expressions::Variable("u"));
+	auto v5 = expressions::VariablePointer(new expressions::Variable("v"));
+	auto v6 = expressions::VariablePointer(new expressions::Variable("w"));
+
+	auto f1 = expressions::ForAllPointer(new expressions::ForAll);
+	auto f2 = expressions::ForAllPointer(new expressions::ForAll);
+
+	auto d = expressions::DummyPointer(new expressions::Dummy("a"));
+
+	f1->variables() = {v1, v2, v3};
+	f2->variables() = {v4, v5, v6};
+
+	f1->setArgument(f2);
+	f2->setArgument(d);
+
+	std::stringstream output;
+	f1->normalized()->print(output);
+
+	ASSERT_EQ(output.str(), "(forall (?x ?y ?z ?u ?v ?w) (a))");
+}