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: Delayed asystolic cardiac arrest after diltiazem overdose ; resuscitation with high dose intravenous calcium .
### Output Text:
Delayed asystolic cardiac arrest after <span class="chemical">diltiazem</span> overdose ; resuscitation with high dose intravenous <span class="chemical">calcium</span> . 