Here is what I have found while searching the web :Originally Posted by esteiber
agreement by proximity.
Certain grammatical constructions provide further complications. Sometimes the noun that is adjacent to the verb can exert more influence than the noun that is the grammatical subject. Selecting a verb in a sentence like A variety of styles has been/have been in vogue for the last year can be tricky. The traditional rules require has been, but the plural sense of the noun phrase presses for have been. While 59 percent of the Usage Panel insists on the singular verb in this sentence, 22 percent actually prefer the plural verb and another 19 percent say that either has or have is acceptable, meaning that 41 percent find the plural verb with a singular grammatical subject to be acceptable.
Taking into consideration the traditional grammar rules I would choose a singular verb , although "a variety of" is attributively used, and "measures" should be considered the real subject of the sentence .Let me put it the other way: Measures of a large variety were taken....the verb is undoubtedly in the plural.
I would like to see some experts` advice on this problem.