4-(2-Hydroxy-1-naphtylazo)-3-hydroxy-1-naphthalenesulfonic acid

3-Hydroxy-4-(2-hydroxy-1-naphtylazo)-1-naphthalenesulfonic acid

1-(2-Hydroxy-1-naphtylazo)-2-hydroxynaphthalene-4-sulfonic acid

3-hydroxy-4-[(2-hydroxynaphthyl)azo]naphthalene-1-sulphonic acid

4-[(2-Hydroxy-1-naphtyl)azo]-3-hydroxy-1-naphthalenesulfonic acid

3-Hydroxy-4-[(2-hydroxy-1-naphtyl)azo]-1-naphthalenesulfonic acid