May plan reference elapsed time regulations?

[Guest tonjer]

I have a client that maintains a church plan. The client regularly acquires new organizations and wants to credit eligibility and vesting service for employees which worked at newly acquiried entities prior to the entities' participation in the plan based on the elapsed time method. May the plan simply state something along the lines of the following: "vesting service will be determined in accordance with the “elapsed time method” of calculating service pursuant to Treasury Regulation Section 1.410(a)-7(a)(1)(ii)" or must the plan fully explain the elapsed time method?