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 results indicate that the clinical usefulness of direct , peripherally acting sub - type - selective alpha1 - adrenoceptor agonists in the medical treatment of stress incontinence may be limited by associated piloerection and cardiovascular side effects .
### Output Text:
The results indicate that the clinical usefulness of direct , peripherally acting sub - type - selective alpha1 - adrenoceptor agonists in the medical treatment of stress incontinence may be limited by associated piloerection and cardiovascular side effects . 