Revolutions can be periodic.Logical formLearned from15 sentences. A contributor can be periodic.Logical formLearned from15 sentences. A grating can be periodic.Logical formLearned from15 sentences. Actions can be periodic.Logical formLearned from15 sentences. (Power outages) can be periodic.Logical formLearned from15 sentences. A fee can be periodic.Logical formLearned from15 sentences. A re-examination can be periodic.Logical formLearned from15 sentences. A rest can be periodic.Logical formLearned from15 sentences. A preventive maintenance can be periodic.Logical formLearned from15 sentences. A response can be periodic.Logical formLearned from15 sentences. A talk can be periodic.Logical formLearned from15 sentences. A display can be periodic.Logical formLearned from15 sentences. (Ice ages) can be periodic.Logical formLearned from14 sentences. Crystals can be periodic.Logical formLearned from14 sentences. Perturbations can be periodic.Logical formLearned from14 sentences.