[Publib] Need book title

[Faulkner, David]

I posted the following query to Project Wombat without any luck. I'm
hoping you of you here can help out our customer.

She is trying to remember the name of a children's book she read in the
60s. She believes it was written in the 40s or 50s. It was about a girl
named Sue and her sister Laura. Their father was the super of the
building in which they lived. They were friends with two immigrant
children, Magda and Anton, whose father was the janitor for the same
building. The children would go on adventures to the Central Park zoo
and other places. There was also a mean lady who lived in the apartment
below that would bang on the ceiling with a broom if they got too noisy.
The book had black and white illustrations with heavy lines.

Thanks for your help!

David
Austin, TX