Located in the posterior wall of the right auricle just below the opening of the superior vena cava, the sino-auricular node (SA node) is a small crescentic node of specialized muscle of about 3 mm in width and 1 cm in length.

Freda, the German undermatron, once discovered him sunbathing nude in the spinney.

21 and 84 are congruent to each other modulo 9, since both numbers leave the same remainder, 3, when divided by 9.

1682, John Dryden, Mac Flecknoe