Ballard, Robert D.. "Foreword". Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions, Princeton: Princeton University Press, 2001, pp. ix-x. https://doi.org/10.1515/9781400842858-001
Ballard, R. (2001). Foreword. In Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions (pp. ix-x). Princeton: Princeton University Press. https://doi.org/10.1515/9781400842858-001
Ballard, R. 2001. Foreword. Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions. Princeton: Princeton University Press, pp. ix-x. https://doi.org/10.1515/9781400842858-001
Ballard, Robert D.. "Foreword" In Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions, ix-x. Princeton: Princeton University Press, 2001. https://doi.org/10.1515/9781400842858-001
Ballard R. Foreword. In: Volcanoes in Human History: The Far-Reaching Effects of Major Eruptions. Princeton: Princeton University Press; 2001. p.ix-x. https://doi.org/10.1515/9781400842858-001