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_This book was ready in October 1916, but the war delayed its
publication. A few alterations have now been made in order to bring
it up to date. It is needless to say how welcome will be further
suggestions, especially for the bibliography. Only by such help can a
book of this kind become useful, since its object is not to expatiate
upon schools and theories but to give with as much accuracy as possible
the main facts concerning the work and life of each individual author._