Definition 6

Let $p: X\rightarrow B$ be a continuous mapping. One says that the mapping $p$ is universally strict if for every cartesian square

${X'}^{f'}$ X

$p'p$

${B'}^f$ B

the mapping $p'$ is strict.

A universally strict mapping is strict. With the notations of Definition 6, if the mapping $p$ is universally strict, the same is true of $p'$. This results immediately from def. 6 and prop. 7 of I, p. 15.