Andreas Blass and Saharon Shelah. Ultrafilters with small generating sets. Israel journal of mathematics, vol. 65 (1989), pp. 259–271. - Andreas Blass and Saharon Shelah. There may be simple - and -points and the Rudin–Keisler ordering may be downward directed. Annals of pure and applied logic, vol. 33 (1987), pp. 213–243. - Andreas Blass. Near coherence of filters. II: Applications to operator ideals, the Stone–Čech remainder of a half-line, order ideals of sequences, and the slenderness of groups. Transactions of the American Mathematical Society, vol. 300 (1987), pp. 557–581. - Andreas Blass and Saharon Shelah. Near coherence of filters III: a simplified consistency proof. Notre Dame journal of formal logic, vol. 30 (1989), pp. 530–538. - Andreas Blass and Claude Laflamme. Consistency results about filters and the number of inequivalent growth types. The journal of symbolic logic, vol. 54 (1989), pp. 50–56. - Andreas Blass. Applications of superperfect forcing and its relatives. Set theory and its applications. Proceedings of a conference held at York University, Ontario, Canada, Aug. 10–21, 1987, edited by J. Steprāns and S. Watson, Lecture notes in mathematics, vol. 1401, Springer-Verlag, Berlin etc. 1989, pp. 18–40. - Andreas Blass and Saharon Shelah. Ultrafilters with small generating sets. Israel journal of mathematics, vol. 65 (1989), pp. 259–271.