Boyer also writes that "the works of Bradwardine had contained some fundamentals of trigonometry gleaned from Muslim sources". Yet "Bradwardine and his Oxford colleagues did not quite make the breakthrough to modern science" (Cantor 2001, p. 122). Al-Kindi in particular seemed to influence Bradwardine, though it is unclear whether this was directly or indirectly. Nonetheless, Bradwardine's work bears many similarities to the work of Al-Kindi, Quia primos (or De Gradibus). The most essential missing tool was calculus.