We are highly indebted to many of our colleagues for their contribution to this work.

Firstly a word of thanks to those who, at IFP Energies nouvelles (IFPEN) contributed directly (review, assistance in computing): Jean Francois Nauroy, Laurence Nicoletis, Noalwenn Dubos-Sallée and Olivier Vincké.

At IFPEN Rock Physics Laboratory, a lot of work was done by PhD students and Interns. Many quotes in this book are testimony to the contribution of Rob Arts, Louanas Azoune, Ana Bayon, Thierry Cadoret, Nathalie Lucet, Didier Martin, Bruno Pouet, Hocine Tabti, Pierre Tarif. For many years, Michel Masson was of great help for the experiments.

The Rock Acoustics courses taught at IFP School and at the Universities Pierre et Marie Curie and Denis Diderot of Paris, and the numerous questions of the students have greatly stimulated the writing of this book.

We are indebted to many of our colleagues (or professors!) for the indirect but invaluable contributions made over the years during discussions or collaborative works. We are grouping them according to their institutions:

• IFPEN: Olga Vizika, Gérard Grau, Christian Jacquin
• Beicip-Franlab: Bernard Colletta
• IPGP and French Universities: Maria Zamora, Mathias Fink, Daniel Royer, Jean-Paul Poirier, Daniel Broseta, André Zarembowitch, Michel Dietrich, Pascal Challande
• IRSN: Justo Cabrera, Philippe Volant
• Stanford University: Amos Nur, Gary Mavko
• Colorado School of Mines: Mike Batzle, Manika Prasad
• Oil and Service companies (CGG, GdFSuez, Petrobras, Schlumberger, Statoil, Shell, Total): Ivar Brevik, Lucia Dillon, Dominique Marion, Eric De Bazelaire, Christian Hubans, Jean Arnaud, Colin Sayers, Thierry Coléou, Arnoult Colpaert, Ronny Hofmann, Mark Kittridge, Salvador Rodriguez.

We wish to express our deepest gratitude to Klaus Helbig for longtime collaboration on Seismic Anisotropy, and even far beyond. Also, within the global community of volunteering Anisotropists, special mention goes to the late Mike Schoenberg, Ivan Psencik, Evgeny Chesnokov, Leon Thomsen, Erling Fjaer, Joe Dellinger, Véronique Farra, Boris Gurevich, Michael Slawinski, and Ilya Tsvankin.

Paul Johnson, of Los Alamos National Laboratory, introduced us to the frightning field of Nonlinear Elasticity. We gratefully acknowledge him and the active community of Nonlinear Elasticity in Geomaterials, including Tom Shankland, Jim TenCate, Koen Van den Abelee, Katherine McCall, Robert Guyer, for long time and fruitful collaboration.

Thanks to Lionel Jannaud, inspired by the great pioneering seismologist Keiti Aki in his work on wave propagation in random media, for allowing us to use some of his results for the writing of Chapter 5 on Frequency/wavelength dependence.

Finally we would like to give special thanks to Thierry Bourbié. This book is an offshoot of our first textbook "Acoustics of Porous Media", and we gained great experience from him.