Although cottage industries, both in "boyar" and peasant households, were still the main source of clothing, food and construction, specialized production, such as weaving and pottery, started to develop by the middle of the 15th century. The first oil wells went into production in 1440, but their oil was also only for household use. In Moldavia, Gypsy slaves were first mentioned in 1428 when Alexander I awarded 31 Gypsy families to the Bistriţa Monastery. In time Gypsies became specialized in several crafts: for example, throughout the Middle Ages the working of iron was an occupation reserved almost exclusively for them.