Rare Rocks in the megalithic monuments of Vale de Rodrigo, Portugal = Rocas raras en los monumentos megalíticos de Vale de Rodrigo, Portugal - Kalb, Philine (Exploring time and matter in Prehistoric monuments : absolute chronology and rare rocks in European megaliths : proceedings of the 2nd European Megalithic Studies Group meeting (Seville, Spain, November 2008) = Explorando el tiempo y la materia en los monumentos prehistóricos., 2011)