LU (http://www.lojban.org/en/publications/reference_grammar/chapter19.html)

Indicates the beginning of a quotation (a sumti) which is grammatical only if the
quoted material also forms a grammatical Lojban text. Terminated by LIhU.

mi cusku lu mi klama le zarci li'u I express [quote] I go-to the market [end
quote].

