In what episode do Mark Greene and Elizabeth Corday hook up for the first time?

In the episode 'Rites of Spring' (Season 5, Episode 19) Mark and Elizabeth try to attend a medical conference. They get হারিয়ে গেছে in the building and accidentally crash a wedding. When they're sure their too late for her presentation Mark asks her to dance the tango with him at the wedding party. This is the start of their relationship.

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I'm not sure what episode is exactly, but Elizabeth's first appearance was in season 4. Maybe this happened around late season 4, early season 5?

I found this that might help, in ER headquarters:
"Season 5
Mark and Elizabeth Corday start dating."
link


Hope this useful :)
I'm going to try and look for the exact episode ;)