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: BACKGROUND & AIMS : Progress in the understanding of susceptibility factors to drug - induced liver injury ( DILI ) and outcome predictability are hampered by the lack of systematic programs to detect bona fide cases .
### Output Text:
BACKGROUND & AIMS : Progress in the understanding of susceptibility factors to drug - induced liver injury ( DILI ) and outcome predictability are hampered by the lack of systematic programs to detect bona fide cases . 