Simplify the following text for a Grade 11 native English-speaking person.
Original: For example , the oases of Awjila , Ghadames and Kufra , situated in modern-day Libya , have at various times been vital to both North-South and East-West trade in the Sahara .
Simplified: For example , the oases of Awjila , Ghadames and Kufra , in modern-day Libya , have at various times been vital to both North-South and East-West trade in the Sahara desert .