Dr. Seuss books with publication dates earlier than indicated on first guide:

Bartholomew and the Oobleck in 1949 and not 1959

The Cat in the Hat Comes back in 1958 and not 1968

Yertle the Turtle and Other Stories in 1950 and not 1958

Gerald McBoing Boing was published in 1951

Books by Theodor Seuss Geisel writing as Theo. Leseig were illustrated by another artist:

Ten Apples Up On Top (1961); illustrated by Roy McKie

I Wish I Had Duck Feet (1965); illustrated by B. Tobey

Come Over To My House (1966); illustrated by Richard Erdoes

The Eye Book (1968); illustrated by Joe Mathieu

In A People House (1972); illustrated by Roy McKie

Wacky Wednesday (1974); illustrated by George Booth

Would You Rather Be a Bullfrog? (1975); illustrated by Roy McKie

Hooper Humperdink? Not Him (1976); illustrated by Charles E. Martin

Please Try To Remember the First of Octember! (1977); illustrated by Art Cummings

Maybe You Should Fly a Jet! Maybe You Should Be a Vet! (1980); illustrated by Michael J. Smollin

The Tooth Book (1981); illustrated by Roy McKie

The Tooth Book (2002); illustrated by Joe Mathieu (posthumous)

AND in 1975, writing as "Rosetta Stone" Geisel wrote:

Because a Little Bug Went Ka-choo! (illustrated by Michael Frith)

Since his 1991 death, there have been a few books based on his previous work or published from notes and sketches found among his papers:

(The Tooth Book, see above, but with an illustrator different from the 1981 edition)

Daisy Head Mayzie (1995)

My Many Colored Days (1996)

Hooray For Diffendoofer Day! (1998); finished by Jack Prelutsky and Lane Smith

(The Green Eggs and Ham Cookbook (2006)

Your Favorite Seuss: A Baker's Dozen By the One and Only Dr. Seuss (2004)

A Hatful of Seuss: Five Favorite Dr. Seuss Stories (1997)

and other compendiums; plus other versions of his classics, such as the Nursery Collection and on and on) . . . Please feel free to correct any errors or let me know wrong information ...