The phrase "are closely based on" is correct and usable in written English.
You can use it to indicate that something is derived from or heavily influenced by another source.
Example: "The film's storyline and characters are closely based on the novel written by the acclaimed author."
Alternatives: "are heavily influenced by" or "are largely derived from".
These are closely based on the recommendations of the Basle Committee, which is trying to modernise its regulations.
But all the other stories we are adapting are closely based on existing books," said Ileen Maisel, of Amber Entertainment, the production company making the films in collaboration with Tesco.
"Three Tall Women" involves a conversation between three characters, A, B, and C, who are closely based on Albee's mother at three different ages: ninety-two (A), fifty-two (B), and twenty-six (C).
The scenes are closely based on photographs taken by Paul Fusco, a photojournalist who was aboard the train and show Americans of different ages, races and demographics in settings variously pastoral, banal and gritty.
And her sleeveless attire (Natia Sirbiladze's costumes are closely based on the New York City Ballet originals, with slight differences of color and pattern) ungallantly draws attention to the muscular looseness under the upper arm that often becomes apparent after the age of 40 in even the most otherwise youthful female dancers.
These existing documents can help form the basis for a better itinerary for your boss's upcoming road trip, whether it's just for a rough comparison or if there happen to be actual parts of the document that are closely based on the template.
The questionnaire will be closely based on the one used by the Oxford Vaccine Group OVGG) in previous typhoid studies to explore participants' study experience.
Maybe he was right, if the people were Western, because Esperanto is closely based on Indo-European languages, or the ones that Zamenhof knew best.
Greene's central character is closely based on him.
The King is closely based on the life of Naser al-Din Shah Qajar, who ruled Persia from 1848 to 1896.
It is easy to forget that the novel was closely based on a real place and time.
