233/264 Notes to the 2017 consolidated financial statements Restricted Stock Awards In connection with the Group’s acquisition of Echo Nest in March of 2014, the Group issued 158,720 restricted stock awards (RSAs) to certain Echo Nest employees. Vesting of the RSAs is contingent on continued employment of these employees. The awards are accounted for as equity­settled share­ based payment transactions. The RSAs vested annually over a two­year period from the acquisition date. In connection with an acquisition during 2017, the Group issued 61,880 RSAs to certain employees of the aquiree. Vesting of the RSAs is contingent on continued employment of these employees. The awards are accounted for as equity­settled share­based payment transactions. The RSAs vest over a two­ and three­year period from the acquisition date. During 2015, 2016, and 2017, the Group recorded share­based compensation expense related to RSAs of €1 million, €0 million, and €0 million, respectively. The valuation of the RSAs was consistent with the fair value of the ordinary shares further described in Note 22. Restricted Stock Unit Program During 2014, the Company implemented Restricted Stock Unit (RSUs) program accounted for as equity­settled share­based payment transaction. RSUs are measured based on the fair market value of the underlying stock on the date of grant. The RSUs granted to participants under the Program generally vest over three to five years. The vesting of certain RSUs could accelerate in the event of an IPO or other change in control event. In June 2017, the shareholders approved the Director Restricted Stock Unit plan for the Company to issue awards specifically to members of its Board of Directors. During 2017, a total of 35,520 RSUs have been awarded under this plan. During 2015, 2016 and 2017, the Group recorded share­based compensation expense related to restricted stock units of €8 million, €5 million, and €6 million, respectively. The valuation of the RSUs was consistent with the fair value of the ordinary shares further described in Note 22. F­40