From the overview:
The 4 quotation marks here are not smart quotes while all the rest of the quotation marks in the document are.
“Similarity transformations (rigid motions followed by dilations) define similarity
in the same way that rigid motions define congruence, thereby formalizing the
similarity ideas of “same shape” and “scale factor” developed in the middle grades.
These transformations lead to the criterion for triangle similarity that two pairs of
corresponding angles are congruent.”