wget https://zenodo.org/record/4596733/files/nptel-valid.tar.gz.partaa
wget https://zenodo.org/record/4596738/files/nptel-valid.tar.gz.partab
wget https://zenodo.org/record/4596742/files/nptel-valid.tar.gz.partac
cat nptel-valid.tar.gz.part*>nptel-valid.tar.gz