Elian, M., AbdelHafiz, I., AbdElReheim, M. (2014). 'PYRIMIDINETHIONES AS BUILDING BLOCKS IN HETEROCYCLIC SYNTHESIS: SYNTHESIS OF PYRANO[2,3-D]PYRIMIDINE, CHROMENO[2,3-D]PYRIMIDINE, PYRIDO[3',2':5,6]PYRANO[2,3-B]PYRIDINE AND PYRIMIDO[5',4':5,6]PYRANO[2,3-D]PYRIMIDINE', Sinai Journal of Applied Sciences, 3(2), pp. 51-62. doi: 10.21608/sinjas.2014.78457