The famous 15th-century Iranian mathematician and astronomer, Jamshı̄d al-Kāshı̄, left his native Kāshān for Samarkand in order to participate in the scientific activity there, upon Air Jordan 9
Ulugh Beg's invitation. Al-Kāshı̄ corresponded in Persian with his father, who lived in Kāshān. One of his letters to his father was published and translated by Kennedy (1960) Jordan Basketball Shoes Canada
and Sayılı (1960). In this paper, we present an English translation with commentary of another letter of al-Kāshı̄ to his father, which has been found recently in Iran. Like the previous one, this new letter contains interesting information on Ulugh Beg's scientific circle in Samarkand.[FORMULA][FORMULA]
Admissible rules of a logic are those rules under which the set of theorems of the logic is closed. In this paper, a Gentzen-style framework is introduced for analytic proof systems that derive admissible rules of non-classical logics. While Gentzen systems for derivability treat sequents as basic objects, for admissibility, the basic objects are sequent rules. Proof systems are defined here for admissible rules of Air Jordan Vancouver classes of modal logics, including K4, S4, and GL, and also Intuitionistic Logic IPC. With minor restrictions, proof search in these systems terminates, giving decision procedures for admissibility in the logics.