We can recommend two hotels in Groningen, the Martini Hotel and the Eden City hotel. Hotels in Groningen tend to fill up quickly, so we advise you to book as early as you can. The two hotels, which are very close to each other, are on walking distance from the central train station and the conference site, see Directions. The rates are similar; around 90 euros for a single and 100 euros for a double room per night, including breakfast.