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: However , the 4 - wk group had a slightly lower accumulation in the right ventricular wall ( 82 % of the control ) and significantly lower accumulation in the left ventricular wall ( about 66 % of the control : p less than 0 . 05 ) .
### Output Text:
However , the 4 - wk group had a slightly lower accumulation in the right ventricular wall ( 82 % of the control ) and significantly lower accumulation in the left ventricular wall ( about 66 % of the control : p less than 0 . 05 ) . 