Following the Fourth Crusade, there was increased contact with the West; and the "lingua franca" of commerce became Italian. In the areas of the Crusader kingdoms a classical education (Greek: παιδεία, "paideia") ceased to be a "sine qua non" of social status, leading to the rise of the vernacular. From this era many beautiful works in the vernacular, often written by people deeply steeped in classical education, are attested. A famous example is the four Ptochoprodromic poems attributed to Theodoros Prodromos. From the 13th to the 15th centuries, the last centuries of the Empire, there arose several works, including laments, fables, romances, and chronicles, written outside Constantinople, which until then had been the seat of most literature, in an idiom termed by scholars as "Byzantine Koine".