litre
Non-SI unit of volume, Math - ei. The other allowed symbol is Math - text.
Source:
Green Book, p. 111
See also:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 979
PAC, 1986, 58, 1405 (Recommendations for the presentation of thermodynamic and related data in biology (Recommendations 1985)) on page 1407