Where can I find the quote in The Catcher in the Rye about how Holden's mother was affected by Allie's death?

There are two direct quotations that mention his mother's condition regarding Allie's death, and one that implies it.

In chapter 15, after Holden makes his date with Sally Hayes, he talks about how irresponsible he is with money.  He then launches into the topic of his father's wealth, and how he's "always investing money in Broadway shows," and that this "drives his mother crazy." At this point, he reveals that his mother "hasn't felt too healthy since [his] brother Allie died. She's very nervous."

Then, in chapter 20, after getting drunk and visiting the Central Park lagoon, Holden fears that he's going to catch "pneumonia and die," and this inspires him to say, "I felt sorry as hell for my mother and father. Especially my mother, because she still isn't over my brother Allie yet."

He goes on to explain that his parents go to the cemetery "quite frequently" to "stick a bunch of flowers on old Allie's grave," further indicating that his mother is still grieving over his younger brother's death.