[procedure] lset<= elt= list1 ...

SRFI-1: Returns true iff every listi is a subset of listi+1, using elt= for the element-equality procedure. List A is a subset of list B if every element in A is equal to some element of B. When performing an element comparison, the elt= procedure's first argument is an element of A; its second, an element of B.

See also lset=.