Read this and answer the question. If the question is unanswerable, say "unanswerable".

The transition from the mandolino to the mandolin began around 1744 with the designing of the metal-string mandolin by the Vinaccia family, 3 brass strings and one of gut, using friction tuning pegs on a fingerboard that sat "flush" with the sound table. The mandolin grew in popularity over the next 60 years, in the streets where it was used by young men courting and by street musicians, and in the concert hall. After the Napoleonic Wars of 1815, however, its popularity began to fall. The 19th century produced some prominent players, including Bartolomeo Bortolazzi of Venice and Pietro Vimercati. However, professional virtuosity was in decline, and the mandolin music changed as the mandolin became a folk instrument; "the large repertoire of notated instrumental music for the mandolino and the mandoline was completely forgotten". The export market for mandolins from Italy dried up around 1815, and when Carmine de Laurentiis wrote a mandolin method in 1874, the Music World magazine wrote that the mandolin was "out of date." Salvador Léonardi mentioned this decline in his 1921 book, Méthode pour Banjoline ou Mandoline-Banjo, saying that the mandolin had been declining in popularity from previous times.

What did Laurentiis de Carmine write?
unanswerable