@incollection{nspuzzlebook,
    type = "incollection",
    author = "Peter Rowlett",
    editor = "Rob Eastaway and Brian Hobbs",
    year = "2023",
    title = {Puzzle 30},
    booktitle = "Headscratchers: The New Scientist Puzzle Book",
    pages = "39, 144-145",
    publisher = "Allen \& Unwin",
    address = "London, U.K."
}