In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: AIMS AND METHODS : We compared the severity of pretransplant illness , psychiatric co - morbidity , medical and psychosocial outcomes of all patients who had undergone liver transplantation ( LT ) emergently between 1999 - 2004 for acetaminophen - induced ALF ( n = 36 ) with age - and sex - matched patients undergoing emergent LT for non - acetaminophen - induced ALF ( n = 35 ) and elective LT for chronic liver disease ( CLD , n = 34 ) .
### Output Text:
AIMS AND METHODS : We compared the severity of pretransplant illness , psychiatric co - morbidity , medical and psychosocial outcomes of all patients who had undergone liver transplantation ( LT ) emergently between 1999 - 2004 for <span class="chemical">acetaminophen</span> - induced ALF ( n = 36 ) with age - and sex - matched patients undergoing emergent LT for non - <span class="chemical">acetaminophen</span> - induced ALF ( n = 35 ) and elective LT for chronic liver disease ( CLD , n = 34 ) . 