Complex sentence: The ideas of this book appeared in his lecture notes from 1884, and encouraged by his students, he worked on this book for the next two decades, but it was not until his exile in India that he finished the first draft.
Split into simpler sentences: The ideas of this book appeared in his lecture notes from 1884. Encouraged by his students, he worked on this book for the next two decades, but it was not until his exile in India that he finished the first draft.