Op 1 maart 2005 heeft [eiser] een arbeidsovereenkomst gesloten met Yamanouchi Europe B.V. voor de functie van General Manager of the Moscow Representative Office in Moskou (de MRO). In de arbeidsovereenkomst zijn de volgende bepalingen vermeld, voorzover voor deze zaak van belang:
“Article 3-Location
The Employee’s place of work will be the offices of YEU-MRO (Yamanouchi, toevoeging kantonrechter), Russia or any other place or places as may be required by the Company from time to time.
(…)
Article 5-Salary
Employee will receive a net base salary of US$ 7,500 fourteen times per calendar year, which will be paid into the Employee’s account, the number be indicated by the employee. (…) Each year it will be considered whether and to what extent the salary will be adjusted as of the 1st of April, starting in 2006. (…)
Article 6-Bonus settlement
The position qualifies for a bonus settlement. Payment of bonus is at the discretion of the Company with no guaranteed payment. (…)
Article 7-Disability
During his disability the employee will receive a payment in accordance with the legal provisions and for the remaining according to the settlements stated in the Supplementary Conditions see Appendix A).
Article 8-Education
The Company will reimburse US$18,000 per annum for private school fees for the employee’s child up to and including high school.(…)
Article 16-Housing
On the first day of employment, the Employee will be entitled to housing allowance of US$8,500 per month net, which will be paid to the Employee’s bank account.(…)