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: Potent DA D1 receptor agents with an intermediate duration of efficacy such as A - 86929 ( approximately 4 hr at higher doses tested ) are potential therapeutic tools in PD and merit further attention .
### Output Text:
Potent <span class="chemical">DA</span> D1 receptor agents with an intermediate duration of efficacy such as <span class="chemical">A - 86929</span> ( approximately 4 hr at higher doses tested ) are potential therapeutic tools in PD and merit further attention . 