The Black Widowers Series Novels

The Return of the Black Widowers (The Black Widowers 6) by Isaac Asimov
Puzzles of the Black Widowers (The Black Widowers 4) by Isaac Asimov
Casebook of the Black Widowers (The Black Widowers 2) by Isaac Asimov
Banquets of the Black Widowers (The Black Widowers 3) by Isaac Asimov
More Tales of the Black Widowers (The Black Widowers 2) by Isaac Asimov
Tales of the Black Widowers (The Black Widowers 1) by Isaac Asimov