I am happy indeed to write a foreword to this book. Since it was founded, the A. F. Ioffe Institute in Leningrad has been in the forefront of semiconductor research. I visited it in 1934, and vividly remember A . F. Ioffe himself and J. Frenkel and their kindness to me, and to others attending the meeting to celebrate the hundredth anniversary of Mendeleev. In the last years my own work on non-crystalline semiconductors has been strongly influenced by the work of B. T. Kolomiets and his co-workers. The English-speaking world should know the great Institute better, and this book will, I am...