MCJ. De haro, JL. Perez-rodriguez, J. Poyato, LA. Perez-maqueda, V. Ramirez-valle, A. Justo, A. Lerf, FE. Wagner: Effect of ultrasound on preparation of porous materials from vermiculite. 2005Applied Clay Science: 30. ISBN 0169-1317 http://dx.doi.org/10.1016/j.clay.2005.02.004