## Textbook Errata and Commentary

I shall make any corrections of errors found in the text in this section. I will also offer some commentary on the text. If you think you have found an error please let me know (e-mail) and I will include it here.

#### Errata and Omissions

• pg. 6 line 5: replace B by "y" in both instances, where y is a block (in B).
• pg. 7 line 11: replace k by "n".
• pg. 11 line 14: replace (1.25) by "(1.33)".
• pg. 12 line -15: replace (1.26) by "(1.35)".
• pg. 19 line 10: replace "q = 16 or q 64" by "q 16".
• pg. 26 line 8: replace (1.34) by "(1.43)".
• pg. 39 line 1: replace (μ - λ)2 - 4(k - μ) by "(μ - λ)2 + 4(k - μ)".
• pg. 39 line 7: replace and, if A by "and, if Γ".
• pg. 40 line -6: replace positive definite by "positive semidefinite".
• pg. 43 line 5: replace design by "2-design".
• pg. 43 line -3: replace at least four by "at least five".
• pg. 50 line 12: in (b) of description, there should be a ½ before the summation.
• pg. 62 line -11: replace inequality by "equality".
• pg. 63 line 4: replace (4.11) by "(4.9)".
• pg. 63 line -14: replace (d)-(g) by "(d)-(h)".
• pg. 63 line -11: replace (2.4) by "(2.5)".
• pg. 63 line -6: replace (2.4) by "(2.5)".

#### Commentary

pg.5 Definition (1.17) : As the authors mention, the term square is not standard. In fact, it is highly non-standard. The authors are trying to get the community of design theorists to give up some poorly chosen terminology and replace it by reasonable choices. This has tried in the past to no avail (the authors mention Dembowski's attempt - also a failure). The term they are trying to displace here is symmetric, but this is well entrenched in the literature, even though there is very little symmetry in a symmetric design.

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