Original: His two famous works , Teatro critico universal ( 1726-1739 ) and Cartas eruditas y curiosas , are multi-volume collections of essays that cover a range of subjects , from education , law , and medicine , to superstitions and popular beliefs .
Simplified: His two famous multi-volume collection of essays , Teatro critico universal ( 1726-1739 ) and Cartas eruditas y curiosas cover a range of subjects , from education , law , and medicine , to superstitions and popular beliefs .