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: Administration of flutamide , letrozole or tamoxifen significantly impaired the memory in intact rats , and significantly attenuated the testosterone replacement in improving STZ - and castration - induced memory impairment .
### Output Text:
Administration of <span class="chemical">flutamide</span> , <span class="chemical">letrozole</span> or <span class="chemical">tamoxifen</span> significantly impaired the memory in intact rats , and significantly attenuated the <span class="chemical">testosterone</span> replacement in improving <span class="chemical">STZ</span> - and castration - induced memory impairment . 