Originally published in hardcover by Random House Children's Books in 2007 Originally published in hardcover: New York : Random House Children's Books, 2010 Originally published as Polar babies by Random House Children's Books, 2000. Originally published in hardcover by Harcourt Children's Books, 1993 Originally published in hardcover: Harcourt Children's Books, 2005 Originally published: New York : Random House Children's Books, 2019 Originally published in paperback by Random House Children's Books, New York, in 1974 Originally published in hardcover by the Blue Sky Press in 2006 Originally published in Great Britain by Penguin Random House Children's in 2018 Originally published : London : Meadowside Children's Books, 2004.