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: It was also evident that , by titrating the dose to achieve a maximum tolerated dose , malformations that normally occur at low incidence , as reported from previous single dose studies , could also be induced with ASA given at multiple doses .
### Output Text:
It was also evident that , by titrating the dose to achieve a maximum tolerated dose , malformations that normally occur at low incidence , as reported from previous single dose studies , could also be induced with <span class="chemical">ASA</span> given at multiple doses . 