LOGO! 8: A Practical Introduction, with Circuit Solutions and Example Programs: Kruse, Stefan: 0781349211721: Amazon.com: Books
Siemens 6ES7 231-4HF32-0XB0 SIMATIC S7-1200, Analog Input, SM 1231, 8 AI, 10V, 5V, -2.5V, OR 0-20MA/4-20 MA, 12 BIT + Sign OR (13 BIT ADC): Amazon.com: Industrial & Scientific
Siemens, 6ES7-153-2BA02-0XB0, SIPLUS S7-300 SM 331 8AI 40-Pole with conformal Coating: Amazon.com: Industrial & Scientific