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: There were no differences in the clinical backgrounds of the patients with and without Tdp other than LAD and age , which were larger and older in the patients with Tdp .
### Output Text:
There were no differences in the clinical backgrounds of the patients with and without Tdp other than LAD and age , which were larger and older in the patients with Tdp . 