Google calendar, sharing, user identification

I am working on simple application which creates google calendar (under it's own account). I want to share this calendar to other users, but I don't know how to identify them (scope user). I have authenticated them with google openid, so I have their openid identifier, but calendar sharing requires some google id, which I 开发者_如何学Cdon't have. Where/how can I obtain it?

Solution found and easy - when authenticating user with oauth, there is possibility to get users e-amil. This is exactly the email address of the account, which was used for authentication = exactly what we need.