Graduate student Andrew Bayles, Professor Aaron Kaplan and Assistant Professor (Lecturer) Abby Kaplan have published a paper in Glossa: A Journal of General Linguistics. You can read the paper, titled "Inter- and intra-speaker variation in French schwa" at the link below.
Bayles, A., Kaplan, A., & Kaplan, A. (2016). Inter- and intra-speaker variation in French schwa. Glossa: a journal of general linguistics, 1(1), 19. DOI: http://doi.org/10.5334/gjgl.54