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 findings were similar to those in early membranous glomerulonephritis , differences being observed however in the results of staining for the early - acting complement components C1q and C4 .
### Output Text:
The findings were similar to those in early membranous glomerulonephritis , differences being observed however in the results of staining for the early - acting complement components C1q and C4 . 