Richard Russell, who shared his technical analysis with subscribers through the influential Dow Theory Letters since 1958, has died. He was 91.

He died Nov. 21 at his home in La Jolla, California, his family said in a message to subscribers on the publication’s website. He had entered a hospital a week earlier and was diagnosed with blood clots in his leg and lungs “and other untreatable ailments,” his family said. He returned home under hospice care.

An adherent of the investing principles of Charles Dow, founder of the Wall Street Journal, Russell published his newsletter continuously from 1958, never missing an issue in more than half a century.