New indications that JD Salinger did indeed leave behind a collection of unpublished manuscripts are given in a freshly unearthed correspondence from the author.

According to the New York Times, the author of The Catcher in the Rye – who published nothing between the 1965 appearance of his novella Hapworth 16, 1924 and his death in 2010 – referred to "my manuscripts" in a 1982 letter to his old friend E Michael Mitchell. A letter to Mitchell in 1994 saw Salinger mention again that he was continuing to write. "I work on," he wrote. "Same old hours, pretty much."

The three newly discovered letters to the late Mitchell, who created the dust jacket for the first edition of The Catcher in the Rye, were found by his girlfriend, Ruth E Linke. She has now sold them to the Morgan Library and Museum where 11 other letters from Salinger to his friend also reside.

Among other things, they see the author writing of how he had to try hard "not to gag" while attending a graduation ceremony. "I've been going to graduations, and there isn't much that I find more pretentious or irksome than the sight of 'faculty' and graduates in their academic get-ups," he wrote in June 1982. A trip to Europe in 1994 warranted a description of Kafka's Prague house as "a tourist trap", and a complaint about the impossibility of finding "a decent, huge green salad" in European cities.

The letters, reported the New York Times, are full of "regular-guy" comments from Salinger: he refers to his friend as "Buddyroo" and himself as "moron that I am". Finding it hard to hear, the author writes that he needs subtitles when watching television – unless he is watching The Thirty-Nine Steps, which "I probably know by heart". "Would that captions went with people's foreheads,'' he muses.

A 1995 postcard, meanwhile, "can be described as an ode to cats", said the New York Times, with Salinger writing "sometimes I can't remember what I saw in Dogs for so many years."