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: Acute toxic dosage - dependent behavioral effects of caffeine were compared in adult males from seven inbred mouse strains ( A / J , BALB / cJ , CBA / J , C3H / HeJ , C57BL / 6J , DBA / 2J , SWR / J ) .
### Output Text:
Acute toxic dosage - dependent behavioral effects of <span class="chemical">caffeine</span> were compared in adult males from seven inbred mouse strains ( A / J , BALB / cJ , CBA / J , C3H / HeJ , C57BL / 6J , DBA / 2J , SWR / J ) . 