PROVIDENCE, R.I. (AP) — The obscure book's margins are virtually filled with clusters of curious foreign characters — a mysterious shorthand used by 17th century religious dissident Roger Williams.

For centuries the scribbles went undeciphered. But a team of Brown University students has finally cracked the code.

Historians call the now-readable writings the most significant addition to Williams scholarship in a generation or more. Williams is Rhode Island's founder and best known as the first figure to argue for the principle of the separation of church and state that would later be enshrined in the Bill of Rights.

His coded writings are in the form of notes in the margins of a book at the university's John Carter Brown Library. The nearly 250-page volume, "An Essay Towards the Reconciling of Differences Among Christians," was donated in the 1800s and included a handwritten note identifying Williams as the notes' author — though even that was uncertain at first....