San Pietro and Sant'Antioco, located in the extreme south west of Sardinia, the local population speaks a variant of Ligurian called Tabarchino (tabarchin); fewer and fewer people speak Venetian, Friulian and Istriot in Arborea and Fertilia, since these villages have been populated in the 1920s and 1930s by mainland colonists who came from northeastern Italy, and families from Istria and Dalmatia immediately after World War II. Due to the Italian assimilation policies carried out since the late 18th century and the ongoing absorption into the Italian culture, over the course of time the once prevalent indigenous language has been increasingly losing ground to Italian and the process of ongoing language shift has led to its endangerment. In fact, according to the data published by ISTAT in 2006, 52.5% of the Sardinian population speaks only Italian in the family environment, while 29.3% alternates Italian and Sardinian and only 16.6% uses Sardinian or other non-Italian languages; outside the circle of family and friends, the last option drops to 5.2%. The resulting Italianization has led to a steep decline of the Sardinian language as well as produced a new non-standard variety of today's majority idiom, Italian: regional Italian of Sardinia (, IrS). Following the recent growth of the foreign-born population, the presence of other languages, principally Romanian, Arabic, Wolof and Chinese, is also expanding in some urban areas. Literature The first literary work in Sardinian language dates back to the second half of the 15th century: a poem inspired by the life of the holy Porto Torres martyrs by the archbishop of Sassari Antonio Cano. Literary production had a remarkable development in the 16th century, the protagonist was Antonio Lo Frasso, his Los diez libros de Fortuna de Amor is mentioned in the Don Quixote by Miguel de Cervantes. This work is written mainly in Spanish, but there are parts written in Catalan and in the Sardinian language. Multilingualism was a characteristic trait of the islanders of that time, among them Sigismondo Arquer, Giovanni Francesco Fara and Pietro Delitala stood out. Delitala wrote in Italian, then Tuscan, and Gerolamo Araolla in all the three languages (Sardinian, Spanish and Italian). But already in the 17th century there was a total integration in the Iberian world as demonstrated by the works in Spanish of the poets José Delitala y Castelvì, Joseph Zatrillas Vico and the writers Francesco Angelo de Vico and Salvatore Vidal. From 1720,