La qualité du thé ne cesse de diminuer.
The quality of tea is going down.
Le coût du carburant ne cesse d'augmenter.
The cost of petrol keeps on going up.
Tom a parlé sans cesse toute la nuit.
Tom kept talking all night.
FrenchTextbook teaches rules like this, in a full beginner course.
162 lessons, 4,000+ exercises, and 6+ hours of audio.