How many films did Jack Lemmom and Walter Matthau appear together in and what are the films' names?

In 1966 he was teamed up for the first time with Walter Matthau in The Fortune Cookie, a Wilder-directed comedy about a photographer who, at the instigation of an unscrupulous lawyer, fakes the seriousness of an injury in order to defraud an insurance company. Two years later Lemmon and Matthau were cast as Felix and Oscar in The Odd Couple, their best-known film together. The two enjoyed a 34-year friendship until Matthau's death in 2000, working together on 11 films, most of which were produced in the 1990s.
http://www.answers.com/topic/jack-lemmon

The Fortune Cookie (1966) - Harry Hinkle and Willie Gingrich
The Odd Couple (1968) - Felix Unger and Oscar Madison
Kotch (1971) - Joseph P Kotcher and sleeping bus passenger (uncredited)
The Front Page (1974) - Hildy Johnson and Walter Burns
The Gentleman Tramp (1975) - a film about Charlie Chaplin - they narrated
Chaplin (1992) - played themselves in Oscar archive (uncredited)
Grumpy Old Men (1993) - Max Goldman and John Gustafson
The Grass Harp (1995) - Dr Morris Ritz and Judge Charlie Cool
Grumpier Old Men (1995) - Max Goldman and John Gustafson
JFK (1991) - Jack Martin and Senator Long
The Odd Couple II (1998) - Felix Unger and Oscar Madison
Out To Sea (1997) - Herb Sullivan and Charlie Gordon

https://en.wikipedia.org/wiki/Jack_Lemmon_and_Walter_Matthau
https://www.indiewire.com/features/general/10-acting-partnerships-that-span-multiple-films-261652/

Also "Buddy Buddy" (1981) as Victor Clooney and Trabucco, a hitman (of all things). Rather an odd film.