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: Only a handful of cases of ATRA - induced myositis in children have been reported , and none in the radiology literature .
### Output Text:
Only a handful of cases of <span class="chemical">ATRA</span> - induced myositis in children have been reported , and none in the radiology literature . 