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: OBJECTIVE : To assess lymphocyte reactivity to dilevalol and to serum containing putative ex vivo dilevalol antigens or metabolites in a case of dilevalol - induced liver injury .
### Output Text:
OBJECTIVE : To assess lymphocyte reactivity to <span class="chemical">dilevalol</span> and to serum containing putative ex vivo <span class="chemical">dilevalol</span> antigens or metabolites in a case of <span class="chemical">dilevalol</span> - induced liver injury . 