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: The results indicate that aniracetam improves cognitive functions which are impaired by different procedure and in different phases of the learning and memory process .
### Output Text:
The results indicate that <span class="chemical">aniracetam</span> improves cognitive functions which are impaired by different procedure and in different phases of the learning and memory process . 