“定期地”用英语怎么说？

他不定期地来探访我们.He visits us at irregular intervals.村民委员会将村务定期或不定期地向村民公开.Villagers'committees regularly or periodically make public the affairs of the village to the villagers.伦敦州管辖范围内有许多站定期地监测大气污染.There was a number of ...