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: Soon after the introduction of ACE inhibitors , acute bouts of angio - oedema were reported in association with the use of these drugs .
### Output Text:
Soon after the introduction of <span class="chemical">ACE inhibitors</span> , acute bouts of angio - oedema were reported in association with the use of these drugs . 