* The Giving Tree by Shel Silverstein (1964)
* Corduroy by Don Freeman (1968)
* Where the Wild Things Are by Maurice Sendak (1963)
* The Very Hungry Caterpillar by Eric Carle (1969)
* Click, Clack, Moo: Cows That Type by Doreen Cronin (2000)
She has also illustrated books for adults, such as The Little Prince by Antoine de Saint-Exupéry.
It's worth noting that there is no author named "Ghita Orth" in any major literary databases. It's possible you're thinking of a different name or have a misspelling.
If you have more information about the specific works you're looking for, I may be able to help you identify the author.