Dictionary.net

• has anterior belly of omohyoid in front, posterior belly of digastric above, and sternomastoid behind.

1898 - American pocket medical dictionary
By Willam Alexander Newman Dorland

• The space bounded by the anterior belly of the omohyoid muscle, the posterior belly of the digastricus and the sternomastoid.

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe