Maryanthe Malliaris and Saharon Shelah, Cofinality spectrum problems in model theory, set theory and general topology . Journal of the American Mathematical Society, vol. 29 (2016), pp. 237-297. - Maryanthe Malliaris and Saharon Shelah, Existence of optimal ultrafilters and the fundamental complexity of simple theories. Advances in Mathematics, vol. 290 (2016), pp. 614-681. - Maryanthe Malliaris and Saharon Shelah, Keisler's order has infinitely many classes. Israel Journal of Mathematics, to appear, https://math.uchicago.edu/∼mem/

H. Jerome Keisler. Maryanthe Malliaris and Saharon Shelah, Cofinality spectrum problems in model theory, set theory and general topology . Journal of the American Mathematical Society, vol. 29 (2016), pp. 237-297. - Maryanthe Malliaris and Saharon Shelah, Existence of optimal ultrafilters and the fundamental complexity of simple theories. Advances in Mathematics, vol. 290 (2016), pp. 614-681. - Maryanthe Malliaris and Saharon Shelah, Keisler's order has infinitely many classes. Israel Journal of Mathematics, to appear, https://math.uchicago.edu/∼mem/. Bulletin of Symbolic Logic, 23(1):117-121, 2017. [doi]