NEW YORK (AP) — Here is a "known known" for publishing this spring: The many aphorisms of former Secretary of Defense Donald Rumsfeld are coming out in book form.

"Rumsfeld's Rules" compiles observations on leadership and organization he has made over his decades spent in government and private business. Broadside Books, a conservative imprint of HarperCollins, announced Wednesday that the book will come out in May and will include new rules and additional commentary from Rumsfeld.

The 80-year-old Rumsfeld, who served as defense secretary under President Ford and President George W. Bush, has a long history of phrasemaking. He called his 2011 memoir "Known and Unknown," a play on his declaration during a 2002 press conference that the world consisted of "known knowns," ''known unknowns" and "unknown unknowns."