Other Authors

The following paper by one of the greatest, most prolific audio authors
of all time (and my personal hero), Norman H. Crowhurst,
details the earliest reference to blocking distortion solutions I have seen:
Puzzled About Amplifiers?
by Norman Crowhurst, Audio, November 1959
Puzzled About Amplifiers? - (.pdf format)

The groundbreaking paper on ultralinear output stages:
An Ultra-Linear Amplifier
by Hafler and Keroes, Audio Engineering 1951:
An Ultra-Linear Amplifier - (.pdf format)

The new "Isodyne" Phase Splitter
by E.F. Worthen, Audio,  August 1958:
The New "Isodyne" Phase Splitter (.pdf format)

Notes on the Cathodyne Phase Splitter
by Albert Preisman, Audio,  April, 1960:
The Cathodyne Phase Splitter (.pdf format)

You've heard of cathode followers, right? How about this:
The Anode Follower
by Charles P. Boegli, Audio,  December, 1960:
The Anode Follower  (.pdf format)

Harmonic and Intermodulation Distortion:
(Author unknown):
Harmonic and Intermodulation Distortion (.pdf format)

For those of you still confused about how to determine if an amplifier is "class A" or "class AB", here are the definitions from the RCA receiving tube manual.  Note the highlighted sections, in particular, the first section where it says: "This classification depends primarily on the fraction of input cycle during which plate current is expected to flow under rated full-load conditions".   This is not an ambiguous thing, as some would have you believe: 
Amplifier Classes(.pdf format)

And, for those of you who  still  think class AB amplifiers are "class A at lower volumes", read the difference in this next paper, which agrees with the RCA receiving tube manual above:

Amplifier Fundamentals:
From "Special Purpose Oscillators and Amplifiers,
Department of the Army Technical Manual TM11-670, July 1952
(Thanks, Lt. Autry, wherever you are):
Amplifier Fundamentals (.pdf format)

The following paper illustrates both the design of shunt RC networks across the output transformer primary and the use of current feedback to modify the damping factor of an amp:
Zero-Impedance Output Stage:
by Raymond G. Anthes, Audio Engineering, January 1953:
Zero-Impedance Output Stage (.pdf format)

Effect of the Cathode Capacitor on P-P Output Stage:
by Robert M. Mitchell, Audio Engineering, November 1955:
Effect of the Cathode Capacitor on P-P Output Stage (.pdf format)

Cathode Phase Inversion (Schmitt PI)
Journal of  Scientific Instruments 15:100-101 ( 1938) , by O.H. Schmitt, 1937
Cathode Phase Inversion 1 (.pdf format)

Cathode Phase Inversion (Schmitt PI)
Review of Scientific Instruments 12:548 (1941) , by Otto H. Schmitt, 1941
Cathode Phase Inversion 2 (.pdf format)

Variable Damping Factor Control
by Charles A. Wilkins, Audio, September 1954
Variable Damping Factor Control  (.pdf format)

Control of Amplifier Source Resistance
by Charles A. Wilkins, Journal of the Audio Engineering Society, January 1956
Control of Amplifier Source Resistance (.pdf format)

Speaker Damping
by Hermon H. Scott, "Power Amplifiers for Music Reproduction",Journal of the Audio Engineering Society, July 1955
Speaker Damping (.pdf format)

Application of Electric Circuit Analogies to Loudspeaker Design Problems
by Bart N. Locanthi, Journal of the AES reprint from IRE Transactions on Audio, March 1952:
Application of Electric Circuit Analogies to Loudspeaker Design Problems (.pdf format)