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: RESULTS : Patients showed a significant reduction in parent - rated irritability and social withdrawal on the ABC as well as significant improvements in emotional lability and inattention on the Conners ' Parent Rating Scale - - Revised .
### Output Text:
RESULTS : Patients showed a significant reduction in parent - rated irritability and social withdrawal on the ABC as well as significant improvements in emotional lability and inattention on the Conners ' Parent Rating Scale - - Revised . 