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: However , caution is required when cyclophosphamide or anthracyclines such as mitoxantrone are used in patients with a possible underlying heart damage , for example , systemic sclerosis patients .
### Output Text:
However , caution is required when <span class="chemical">cyclophosphamide</span> or <span class="chemical">anthracyclines</span> such as <span class="chemical">mitoxantrone</span> are used in patients with a possible underlying heart damage , for example , systemic sclerosis patients . 