Glossary used in the business of art: after – a direct imitation of an original artwork, made at a later date assistant – someone who worked in the artist's studio assistants – by the artist, made with help from his assistants associate of – by someone who had links to the artist, but was not in their studio attributed to – thought to have been painted by the artist, but there is a degree of uncertainty after – either by the artist or a direct imitation of the artist's style, made at a later date follower of – either by the artist or by someone who admired them and imitated their style, but was not necessarily a pupil circle of – by an artist closely associated with the master artist, but who did not work in their studio copy after – repetition of another artwork, generally made after the artist's lifetime, or by an artist outside their studio copy of – repetition of another artwork follower of – by someone who admired the artist and imitated their style, but was not necessarily a pupil forgery – imitation of an artwork, intended to deceive imitator of – by someone who admired the artist and their style, but was probably working at a later date possibly – thought to be by the artist, but this is uncertain pupil of – by someone who trained within the studio or workshop of the artist, often profoundly influenced by the artist's style school of – in the general style or manner of student of – by someone who trained within the studio or workshop of the artist, often profoundly influenced by the artist's style studio of – by assistants or pupils who worked in the artist's studio, probably under the direction and guidance of the artist and studio – by the artist, with assistance from his studio studio copy – by pupils in imitation of the master artist. Pupils often copied the artist's most famous works in order to disseminate copies style of – by someone who created the artwork in a manner that resembles the artist Reference to: https://artuk.org/about/glossary-85 In conclusion, when you buy a painting you need to verify the authenticity of the painting by obtaining a COA , certificate of authenticity by the solerecognized authority for an artist. Attributed to, school of, cercle of etc is not a warranty of authenticity.