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: The use of adriamycin ( ADR ) in cancer chemotherapy has been limited due to its cumulative cardiovascular toxicity .
### Output Text:
The use of <span class="chemical">adriamycin</span> ( <span class="chemical">ADR</span> ) in cancer chemotherapy has been limited due to its cumulative cardiovascular toxicity . 