Either the teachers or the principal is (are) to blame for the accident.
I sent this question once. However, it is still unclear to me that in this case which form
is the best to use in careful written standart British English? Inasmuch as according to “Advanced grammar in Use” by Martin Hewings, both the plural and singular verbs are correct in this case, while according to “Understanding and Using English Grammar” by Betty Schrampfer Azar only singular verb is possible.
As far as I know, the explanations in “Advanced Grammar in Use” deal mainly standard modern British English, while the latter deal with American English.
1) Either the students or the teacher is planning to come. (Betty Azar)
2) Either the students or the teacher is/are planning to come. (Martin Hewings)
1) Please tell me which one is more formal?
2) And is there virtually any difference between them in terms of Am.E and Br.E.?