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: Overall survival from the time of OLTX was not significantly different among groups , but by year 13 , the survival of the patients who had ESRD was only 28 . 2 % compared with 54 . 6 % in the control group .
### Output Text:
Overall survival from the time of OLTX was not significantly different among groups , but by year 13 , the survival of the patients who had ESRD was only 28 . 2 % compared with 54 . 6 % in the control group . 