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: Associated studies demonstrated that lometrexol plasma pharmacokinetics were not altered by folic acid administration indicating that supplementation is unlikely to reduce toxicity by enhancing lometrexol plasma clearance .
### Output Text:
Associated studies demonstrated that <span class="chemical">lometrexol</span> plasma pharmacokinetics were not altered by <span class="chemical">folic acid</span> administration indicating that supplementation is unlikely to reduce toxicity by enhancing <span class="chemical">lometrexol</span> plasma clearance . 