diff --git a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Exact_complex.h b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Exact_complex.h
deleted file mode 100644
index ff228aa60c7..00000000000
--- a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Exact_complex.h
+++ /dev/null
@@ -1,145 +0,0 @@
-#ifndef CGAL_EXACT_COMPLEX_H
-#define CGAL_EXACT_COMPLEX_H
-
-#include <iostream>
-#include <CGAL/assertions.h>
-#include <CGAL/number_utils.h>
-
-// Complex number in the form a + bi, where a and b are of type NT.
-// NT must be an exact number type, model of:
-// 		+ FieldWithRootOf
-//		+ RealEmbeddable
-//		+ FromDoubleConstructible
-//
-
-
-namespace CGAL {
-
-template <class NumberType>
-class Exact_complex {
-
-typedef Exact_complex<NumberType> 		Self;
-
-private:
-	NumberType _a, _b;
-
-public:
-	typedef NumberType NT;
-
-	Exact_complex() :
-		_a(0), _b(0) {}
-
-	Exact_complex(NT a, NT b) :
-		_a(a), _b(b) {}
-
-	NT real() const {
-		return _a;
-	}
-
-	void set_real(NT val) {
-		_a = val;
-	}
-
-	NT imag() const {
-		return _b;
-	}
-
-	void set_imag(NT val) {
-		_b = val;
-	}
-
-	Self conj() const {
-		return Self(_a, -_b); 
-	}
-
-	NT square_modulus() const {
-		return (_a*_a + _b*_b);
-	}
-
-	NT modulus() const {
-		return CGAL::sqrt(this->square_modulus());
-	}
-
-	Self reciprocal() {
-		NT denom = _a*_a + _b*_b;
-		if (denom == NT(0)) {
-			return Self(0,0);
-		} else {
-			return Self(_a/denom, -_b/denom);
-		}
-	}
-
-	Self invert_in_unit_circle() {
-		return this->reciprocal().conj();
-	}
-
-	template <class Circle_2>
-	Self invert_in_circle(Circle_2 c) {
-		NT r2 = c.squared_radius();
-		NT xc = c.center().x();
-		NT yc = c.center().y();
-		NT denom = (_a - xc)*(_a - xc) + (_b - yc)*(_b - yc);
-		return Self(xc + r2*(_a-xc)/denom, yc + r2*(_b-yc)/denom);
-	}
-
-
-	Self operator+(const Self& other) const {
-		return Self(this->_a + other._a, this->_b + other._b);
-	}
-
-	Self operator-(const Self& other) const {
-		return Self(this->_a - other._a, this->_b - other._b);
-	}
-
-	Self operator*(const Self& other) const {
-		NT rp = _a*other._a - _b*other._b;
-		NT ip = _b*other._a + _a*other._b;
-		return Self(rp, ip);
-	}
-
-	Self operator/(const Self& other) const {
-		NT denom = other._a*other._a + other._b*other._b;
-		CGAL_assertion(denom != 0);
-		NT rp = _a*other._a + _b*other._b;
-		NT ip = _b*other._a - _a*other._b;
-		return Self(rp/denom, ip/denom);
-	}
-
-
-};
-
-
-template <class NT>
-std::ostream& operator<<(std::ostream& s, const Exact_complex<NT>& c) {
-	s << c.real() << (c.imag() >= 0 ? " + " : " - ") << abs(c.imag()) << "i";
-	return s;
-} 
-
-// just to give an ordering
-template<class NT>
-bool operator==(	const Exact_complex<NT>& lh,
-  					const Exact_complex<NT>& rh)
-{
-  return (lh.real() == rh.real() && lh.imag() == rh.imag());
-}
-
-template<class NT>
-bool operator!=(	const Exact_complex<NT>& lh,
-  					const Exact_complex<NT>& rh)
-{
- 	return !operator==(lh, rh); 
-}
-
-
-// just to give an ordering
-template<class NT>
-bool operator<(	const Exact_complex<NT>& lh,
-  					const Exact_complex<NT>& rh)
-{
-  return lh.square_modulus() < rh.square_modulus();
-}
-
-
-} // namespace CGAL
-
-#endif // CGAL_EXACT_COMPLEX_H
\ No newline at end of file
diff --git a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation.h b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation.h
index 156f4ce8d39..48f8a2be713 100644
--- a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation.h
+++ b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation.h
@@ -25,7 +25,7 @@
 #include <vector>
 #include <CGAL/Hyperbolic_octagon_translation_matrix.h>
 #include <CGAL/Hyperbolic_octagon_translation_word.h>
-#include <CGAL/Exact_complex.h>
+#include <CGAL/internal/Exact_complex.h>
 
 namespace CGAL {
 
diff --git a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation_matrix.h b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation_matrix.h
index 7cd861c1582..297442534bd 100644
--- a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation_matrix.h
+++ b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Hyperbolic_octagon_translation_matrix.h
@@ -19,7 +19,7 @@
 #ifndef CGAL_HYPERBOLIC_OCTAGON_TRANSLATION_MATRIX_H
 #define CGAL_HYPERBOLIC_OCTAGON_TRANSLATION_MATRIX_H
 
-#include <CGAL/Exact_complex.h>
+#include <CGAL/internal/Exact_complex.h>
 #include <CGAL/number_utils.h>
 #include <iostream>
 #include <vector>
diff --git a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Periodic_4_hyperbolic_Delaunay_triangulation_traits_2.h b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Periodic_4_hyperbolic_Delaunay_triangulation_traits_2.h
index 48753192c3f..a8a6b939b17 100644
--- a/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Periodic_4_hyperbolic_Delaunay_triangulation_traits_2.h
+++ b/Periodic_4_hyperbolic_triangulation_2/include/CGAL/Periodic_4_hyperbolic_Delaunay_triangulation_traits_2.h
@@ -31,7 +31,6 @@
 #include <CGAL/predicates_on_points_2.h>
 #include <CGAL/basic_constructions_2.h>
 #include <CGAL/distance_predicates_2.h>
-#include <CGAL/Exact_complex.h>
 #include "boost/tuple/tuple.hpp"
 #include "boost/variant.hpp"
 #include <CGAL/Hyperbolic_octagon_translation.h>