Min Nan texts, all Hokkien, can be dated back to the 16th century. One example is the Doctrina Christiana en letra y lengua china, presumably written after 1587 by the Spanish Dominicans in the Philippines. Another is a Ming Dynasty script of a play called Romance of the Lychee Mirror (1566), supposedly the earliest Southern Min colloquial text. Xiamen University has also developed an alphabet based on Pinyin, which has been published in a dictionary called the Minnan Fangyan-Putonghua Cidian (閩南方言普通話詞典) and a language teaching book, which is used to teach the language to foreigners and Chinese non-speakers. It is known as Pumindian.