title: Reply to the letter by C.J. Fontaine.
authors.affiliation: Institut Calot, rue du Dr-Calot, 62600 Berck-sur-Mer, France. Electronic address: cmorin@hopale.com.
authors.forename: C
authors.initials: C
authors.lastname: Morin
authors.affiliation: Institut Calot, rue du Dr-Calot, 62600 Berck-sur-Mer, France.
authors.forename: C
authors.initials: C
authors.lastname: Ursu
authors.affiliation: Institut Calot, rue du Dr-Calot, 62600 Berck-sur-Mer, France.
authors.forename: C
authors.initials: C
authors.lastname: Delecourt