The commas are necessary. A version without commas would be appropriate in a context involving several events with distinct anniversaries - not very likely:
This sort of context is rare (if just conceivable by people with reality problems ) so some people might feel that - if the sentence is short enough - the commas don't matter too much. I would disagree.Code:The event which celebrates its 30th anniversary puts together two bull (male) camels with a female camel on heat nearby. On the other hand, the event which celebrates its 20th anniversary puts together only one bull (male) camel with a young female camel who is not on heat 100 metres away, and the event which celebrates its 10th anniversary puts together a small cat and a huge rat...
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