Eckehard Julius Petsch

Beryl and Its Color Varieties: Aquamarine, Heliodor, Morganite, Goshenite, Emerald and Red Beryl

Dmitriy Belakovskiy with Lee Van Iderstine, Eckehard Julius Petsch, Peter Huber, Gary Freeman, Guanghua Liu, Jan Kanis, Bruce Jarnot, Roberto Pucci, Peter Lyckberg, Frank Coffa, Federico Pezzotta, Stefan Weiss, Gloria Staebler, William B. Simmons, Tom Wilson, Fred Wilda, Günther Neumeier, Luiz Menezes, Alexander Falster, Michael Wise, Jeff Scovil, John Bradshaw, Kevin Dixon, Adalberto Giazotto, Bruce Cairncross, Dmitriy Belakovskiy, Alfredo Petrov, Thomas Schüpbach, Tony Potucek, Jesse Fisher, WALTER GABRIEL, Mark Jacobson, Paul Balayer, George Rossman, Dermot Henry, Rupert Hochleitner, Dawn Kellett, Emanuela Cucchiari, Miranda Jarnot, Lee Groat