I hope this is the correct place to pose this question, if not, please direct me there.

I am writing a series of historical novels, carrying a plot line from about 1500 through the present day.  Throughout the novels, my characters may encounter other well-known literary characters.

What is the protocol for using another author's character for a brief encounter with your hero in your novel, especially when the author is deceased?

Ex: John D. McDonald's Travis McGee.  One of my characters is getting kicked around down in Florida and T.M. steps in and rescues his butt.  Afterwards, T.M. takes him on board the 'Busted Flush' for a quick fix-up, a drink, and some free advice about not irritating beach bums that outweigh you by 100 pounds of solid muscle.  That's it, in and out of the novel in several short paragraphs.

Whom do you contact to obtain permission to use these characters in such brief scenes?
Do you need to contact anyone when the author's deceased?

Thanks in advance for all responses,

John