1. A Special Purpose Amplifier;Matthews,1934
2. Improvements in or Relating to Thermionic Valve Amplifying Circuit Arrangements;Blumlein,1934
3. Push-Pull Resistance Coupled Amplifiers;Offner,1937
4. A Simple Differential Amplifier;Schmitt;Review of Scientific Instruments,1937
5. Differential Amplifier;Toennies,1938