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: Patients receiving D - penicillamine therapy should be followed carefully for the development of autoimmune complications like polymyositis / dermatomyositis .
### Output Text:
Patients receiving <span class="chemical">D - penicillamine</span> therapy should be followed carefully for the development of autoimmune complications like polymyositis / dermatomyositis . 