Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Course | Distance | Type | Winner |
| --- | --- | --- | --- | --- |
| 20 May | Campione d'Italia | km (mi) | Individual time trial | Charly Grosskost ( FRA ) |
| 21 May | Campione d'Italia to Novara | km (mi) | Plain stage | Eddy Merckx ( BEL ) |
| 22 May | Novara to Saint-Vincent | km (mi) | Stage with mountain(s) | Eddy Merckx ( BEL ) |
| 23 May | Saint-Vincent to Alba | km (mi) | Plain stage | Guido Reybrouck ( BEL ) |
| 24 May | Alba to Sanremo | km (mi) | Stage with mountain(s) | Ward Sels ( BEL ) |
| 25 May | Sanremo to Sanremo | km (mi) | Stage with mountain(s) | Italo Zilioli ( ITA ) |
| 26 May | Sanremo to Alessandria | km (mi) | Stage with mountain(s) | José Antonio Momene ( ESP ) |
| 27 May | Alessandria to Piacenza | km (mi) | Stage with mountain(s) | Guerrino Tosello ( ITA ) |
| 28 May | San Giorgio Piacentino to Brescia | km (mi) | Stage with mountain(s) | Eddy Merckx ( BEL ) |
| 29 May | Brescia to Lido di Caldonazzo | km (mi) | Stage with mountain(s) | Julio Jiménez ( ESP ) |
| 30 May | Trento to Monte Grappa | km (mi) | Stage with mountain(s) | Emilio Casalini ( ITA ) |
| 31 May | Bassano del Grappa to Trieste | km (mi) | Plain stage | Guido Reybrouck ( BEL ) |
| 1 June | Gorizia to Tre Cime di Lavaredo | km (mi) | Stage with mountain(s) | Eddy Merckx ( BEL ) |
| 2 June | Cortina d'Ampezzo to Vittorio Veneto | km (mi) | Stage with mountain(s) | Lino Farisato ( ITA ) |
| 3 June | Vittorio Veneto to Marina Romea | km (mi) | Plain stage | Luigi Sgarbozza ( ITA ) |
| 4 June | Ravenna to Imola | km (mi) | Plain stage | Marino Basso ( ITA ) |
| 5 June | Rest day | Rest day | Rest day | Rest day |
| 6 June | Cesenatico to San Marino ( San Marino ) | km (mi) | Individual time trial | Felice Gimondi ( ITA ) |
| 7 June | San Marino ( San Marino ) to Foligno | km (mi) | Plain stage | Franco Bitossi ( ITA ) |
| 8 June | Foligno to Abbadia San Salvatore | km (mi) | Stage with mountain(s) | Julio Jiménez ( ESP ) |
| 9 June | Abbadia San Salvatore to Rome | km (mi) | Plain stage | Luciano Dalla Bona ( ITA ) |
| 10 June | Rome to Rocca di Cambio | km (mi) | Stage with mountain(s) | Luis Pedro Santamarina ( ESP ) |
| 11 June | Rocca di Cambio to Blockhaus | km (mi) | Stage with mountain(s) | Franco Bitossi ( ITA ) |
| 12 June | Chieti to Naples | km (mi) | Plain stage | Guido Reybrouck ( BEL ) |
| Total | Total | km (mi) | km (mi) | km (mi) |
Question:
Name the date which has type of plain stage
Answer:
21 May, 23 May, 31 May, 3 June, 4 June, 7 June, 9 June, 12 June