Productivity

1913 • 1,269 Readers • 288 pages • 3.9

2008 • 478 Readers • 304 pages • 4.1

1990 • 489 Readers • 336 pages • 4.1

1988 • 549 Readers • 303 pages • 4.1

2012 • 1,016 Readers • 402 pages • 4

2015 • 26 Readers • 83 pages • 4.3