https://www.sciencedirect.com/science/article/pii/S1053811902900145 (Abstract)
Shmuel, A., Yacoub, E., Pfeuffer, J., Van De Moortele, P.-F., Adriany, G., Ugurbil, K., et al. (2002). The Spatial Pattern of the Positive BOLD Response at High Magnetic Field is Approximately Stationary. NeuroImage, 16(2 Supplement 1): 562, 1287.