> 雪国に暮らす上で大変なことは、毎日の雪かきです。

In this phrase why didn't we use の particle after 上で?
CC BY-SA 4.0
2019-07-05T11:15:02.007
69272
2019-07-05T13:11:10.360
2019-07-05T13:11:10.360
34489
question
particle-の
Why isn't の used after 上で here?