. "781.66" . . . "ML3534.W25 2010" . . . "978-0-9796163-3-4" . . "624415373" . . "364"^^ . . . "Mean Deviation: Four Decades of Progressive Heavy Metal"@en . "Mean Deviation: Four Decades of Progressive Heavy Metal is a non-fiction book written by former Metal Maniacs magazine editor Jeff Wagner. The book was illustrated by Voivod drummer Michel \"Away\" Langevin and features a foreword by Porcupine Tree frontman Steven Wilson. Mean Deviation was published in December 2010 by Bazillion Points under supervision of Ian Christe."@en . .