The Wardens and Rangers and later "time wardens" of Poul Anderson's
The Corridors Of Time inhabit a single immutable timeline.
The mutant time travellers of Anderson's There Will Be Time inhabit a different single immutable timeline.
His Time Patrollers believe that they inhabit a single mutable timeline although it is impossible to formulate a coherent account of all the events that are described as occurring in the Time Patrol series.
The patrons of Anderson's Old Phoenix inhabit multiple timelines.
An immense dimensional framework would be necessary to incorporate such diverse scenarios into a single multiverse.
However, we find similar theoretical language and practical examples in the Time Patrol universe and in the Old Phoenix multiverse.
According to a Time Patrol instructor, both instantaneous transportation and travel into the past require infinitely discontinuous functions for their mathematical description and also involve:
"'...the concept of infinitely-valued relationships in a continuum of 4N dimensions, where N is the total number of particles in the universe.'"
-Poul Anderson, "Time Patrol" IN Anderson, Time Patrol (Riverdale, NY, December 2010), pp. 1-53 AT 2, p. 9.
According to Valeria Matuchek:
"'Nobody's proved, in my world, whether there's an infinity of [universes], or whether the number's finite but enormous - N factorial, to be exact, where N is the total number of matter and energy particles that exist....'"
-Poul Anderson, A Midsummer Tempest (London, 1975), xii, p. 101.
OK. "N" means the same in both cases but, in the first case, there is a single continuum with 4N dimensions whereas, in the second case, there are possibly N factorial continua!
Secondly, there is a common practical example.
As far as the Time Patrol is concerned:
"'...suppose I went back and prevented Booth from killing Lincoln. Unless I took very elaborate precautions, it would probably happen that someone else did the shooting and Booth got blamed anyway.'"
-"Time Patrol," 2, p. 15.
And for Valeria:
"'...suppose I happened to meet Abe Lincoln here...given a lot of time together, I probably couldn't resist warning him against Ford's Theater. Lord knows what that might do to his world. Make a new continuum? I'm not sure if that's possible.'"
-A Midsummer Tempest, xi, pp. 93-94.
The host of the Old Phoenix performs the same function as the Time Patrol by preventing conversations that would result in an Abraham Lincoln that was going to be assassinated by Booth not being assassinated by Booth.
And the scenarios have similarities because they have a common creator.
(Lastly, Sheila and I now live on Lincoln Rd, Lancaster.)