--- /dev/null
+#ifndef __VIENNA_RNA_PACKAGE_DUPLEX_H__
+#define __VIENNA_RNA_PACKAGE_DUPLEX_H__
+
+#include "data_structures.h"
+
+/**
+ * \file duplex.h
+ * \brief Duplex folding function declarations...
+ */
+
+
+duplexT duplexfold( const char *s1,
+ const char *s2);
+
+duplexT *duplex_subopt( const char *s1,
+ const char *s2,
+ int delta,
+ int w);
+
+duplexT aliduplexfold(const char *s1[],
+ const char *s2[]);
+
+duplexT *aliduplex_subopt(const char *s1[],
+ const char *s2[],
+ int delta,
+ int w);
+
+#endif