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: Flestolol blood concentrations increased linearly with increasing dose and good correlation exists between blood concentrations of flestolol and beta - adrenergic blockade .
### Output Text:
<span class="chemical">Flestolol</span> blood concentrations increased linearly with increasing dose and good correlation exists between blood concentrations of <span class="chemical">flestolol</span> and beta - adrenergic blockade . 