A Dictionary of Saintly Women, Volume 1 (https://books.google.com/books?id=PBgYAAAAYAAJ&pg=PA413&lpg=PA413&dq=irmgard+zutphen+saint&source=bl&ots=xjvE82bFqM&sig=43kSEuwrS19p8ayKsMCFJzHbDOg&hl=en&sa=X&ved=0ahUKEwjW67CooonWAhWo7IMKHZSyDukQ6AEIKzAB#v=onepage