[einhverfr]

Actually with a [A-Z]. [a-z] that's an easy case.

The harder case is an [A-Z]. [A-Z] which is not a sentence ending. Consider the following:

"When we compare the use of mistakes in speech in the Saga of St. Olaf with some of the other Old Norse literature, we can see that there is, in fact, a pattern of use of errors in speech being a sort of death omen."

The single space there identifies that there is no end of sentence between St. and Olaf. Of course when you are working in LaTeX you have to tell LaTeX that this is a word break and not a sentence break or else it will kern it as an end-of-sentence.