A special stability problem for linear multistep methods by Germund Dahlquist (1963, 10.1007/BF01963532)

Published paper, BIT 3, 27–43; author byline Germund G. Dahlquist. Section 1 gives the constant-coefficient, first-derivative and coprimality assumptions; §2 defines A-stability and proves the order barrier. The university hosts the scan and is not its author.