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Continue to ChatOn parallel timelike ruled surfaces with timelike rulings - https://avesis.ogu.edu.tr/publication/details/2cdc4bfc-9ae0-4484-a77e-c94960d47792/on-parallel-timelike-ruled-surfaces-with-timelike-rulings
On parallel timelike ruled surfaces with timelike rulings - https://avesis.ogu.edu.tr/publication/details/2cdc4bfc-9ae0-4484-a77e-c94960d47792/on-parallel-timelike-ruled-surfaces-with-timelike-rulings