Table:
text: EFDA Nations Cup
Champions
Champions
Season Venue Teams Drivers Champion Second_ Third
1990 Circuit de Spa-Francorchamps 17 34 Portugal ( Pedro Lamy , Diogo Castro Santos ) Brazil Sweden
1991 Circuit Park Zandvoort 18 36 Portugal ( Pedro Lamy , Diogo Castro Santos ) Germany Sweden
1992 Autódromo do Estoril 14 28 Netherlands ( Martin Koene , Jos Verstappen ) Portugal Italy
1993 Autódromo do Estoril 15 30 Austria ( Martin Albrecht , Hubert Stromberger ) Belgium Brazil
1994 Circuit Park Zandvoort 18 36 Netherlands ( Tom Coronel , Donny Crevels ) Austria Portugal
1995 Circuit de Nevers Magny-Cours 15 30 Portugal ( Manuel Gião , André Couto ) Netherlands Great Britain

Question: What is the average season when the venue was Circuit de Nevers Magny-Cours and the riders were 30+ for the EFDA Nations Cup?