who should i ask for my 4th letter of rec?

[frankdux]

so i sorta just made a thread about this already but i'd like to turn it into a poll.

ok, so a few particular programs require a 4th letter. i already have 3 good letter writers to start with. i have a bachelors in math, and a masters in math education. i want to do a phd in applied math with the goal of being a professor. so i'm covering all my bases with the following three people writing me letters:

1. a math professor from my undergrad

2. a math professor from my grad

3. my grad program advisor who was also my student teacher mentor as well as an instructor of mine in 2 classes.

unfortunately i've been unable to establish contact with two other math professors who i think would write good letters for me, and both have already written letters for me in the past. kind of upsetting. anyways, the two people i'm thinking who could write me good letters would be:

1. my supervisor from the year i spent teaching english in japan immediately following my grad program. on one hand, it has nothing to do with math. but on the other hand, it obviously does have something to do with teaching which does have something to do with what i want to do with the rest of my life. (being a prof) also, its a letter from a former employer, which is usually a decent alternative if you have work experience after school.

2. my japanese teacher i had for 4 semesters during my grad program. i got all A's in her classes. also, she has already written a letter for me in the past. again though, it has nothing to do with math, and even less to do with what i want to do with the rest of my life. but at least, she could offer further details into my academic abilities.

i don't know. what do you think?

[frankdux]

thanks for voting, but can someone give me some feedback?

[t_ruth]

I think either of the first two would be fine. You already have two professors writing, why not go with the supervisor?