The twenty-sixth meeting was held February 25-26, 2011, at Northern Kentucky University.  This meeting was a natural follow-up to the previous meeting, continuing a line of reasoning first begun by Ernst Kummer, with his ideal complex numbers.  We undertook a a study of the evolution of the concept of an ideal (in a ring) by reading from Richard Dedekind's first exposition in the Supplement to the 2nd (1871) edition of Dirichlet's Vorlesungen über Zahlentheorie (Lectures on Number Theory). The relevant sections have appeared in a recent English translation by Jeremy Avigad (Carnegie Mellon University). Together with the German originals for this text and the revised texts that Dedekind provided for the 3rd (1879) and 4th (1894) editions of Dirichlet's textbook, we will also draw from two papers by Harold M. Edwards, who wrote extensively on this subject in the early 1980s. Here's a full bibliographic list:

• Richard Dedekind. Supplement X von Dirichlets Vorlesungen über Zahlentheorie, 2. Auflage, 1871.
• Jeremy Avigad. Dedekind's 1871 version of the theory of ideals. Carnegie Mellon Technical Report CMU-PHIL-162, 2004.
• Richard Dedekind. Supplement XI von Dirichlets Vorlesungen über Zahlentheorie, 3. Auflage, 1879.
• Richard Dedekind. Supplement XI von Dirichlets Vorlesungen über Zahlentheorie, 4. Auflage, 1894.
• H.M. Edwards. The genesis of ideal theory. Arch. Hist. Exact Sci. 23, 1980, 321-378.
• H.M. Edwards. Dedekind's invention of ideals. Bull. London Math. Soc. 15 (1), 1983, 8-17.