How can I keep text identical across several text boxes in InDesign CS6?

I have a layout with many (2x2) postcard-size cards on an A4 page, which are going to be cut into individual pieces after print. The postcards should remain identical. Each has multiple text fields. I would like text changed in one of those fields to be automatically updated in the corresponding fields in the other postcards. How do I achieve this?

In the following example, if I change e.g. "Vor genau" in one place, I would like that change to be reflected on the other side as well.