"The Eyes of the Overworld" and "The Dying Earth"

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Overview:

Title: "The Eyes of the Overworld" and "The Dying Earth"
Author: Robert Silverberg
Year: 1980
Type: Essays

Editions/Publications:

Unknown. Jack Vance (Unknown, Robert Silverberg, Taplinger, ISBN-10: 0800842952, $5.95, 252 pages, Trade Paperback, Non-fiction)
Unknown. Jack Vance (Unknown, Robert Silverberg, Taplinger, ISBN-10: 0800842944, $12.95, 252 pages, Hardcover, Non-fiction)