I'm reading David Maier's outstanding but out-of-print book on relational databases (the book,"The Theory of Relational Databases", is available online from the author's website http://web.cecs.pdx.edu/~maier/TheoryBook/TRD.html). I have a question regarding the proof of Theorem 4.2 of Chapter 4. On page 55 of the book (see pdf for Chapter 4 if you don't have the book), it was said that the FDs of step 13 and 14 can be replaced by new steps 13.1 ... 13.k and 14 that follows. It seems to me that only step 13.k is needed and steps 13.1 - 13.(k-1) are unnecessary. I'm pretty sure I'm missing something here, but the author didn't explain. In fact, the example in the proof shows that only step 13.k is used.