The oldest book written in the Americas could be an astronomy text from a Maya civilization hundreds of years ago, PBS reports.

Researchers believe Americas: the Grolier Codex, a guide written by a “diligent scribe” that features personified images of the sun, death and several other deities, is the first book created in the continent.

The title, believed to have been written about 900 years ago, was initially considered a fake, with researchers pointing out “discrepancies in the book’s calendar system, hinting that a forger might have been trying to imitate a calendar he saw in another Maya artifact,” according to ArsTechnica.

However, after further examination, archaeologists determined in 2016 that the Maya book is genuine.

Stephen Houston, a social scientist at Brown University, explains that the discrepancies in the calendars can likely be attributed to regional or temporal variations in the mythology of Venus, which the book centers on.

Researchers say they are certain the book is genuine because radiocarbon dating places the Codex at AD 1257±110 and 1212±40, there aren’t any modern pigments on the book and all other items that were found along with the guide are also authentic, among other arguments.

So there you have it: The Maya are the Americas’ first book authors.