الإتاحة: https://doi.org/10.1002/9780470987100.ch37Test
الإتاحة: https://doi.org/10.1002/9780470987100.ch36Test
الإتاحة: https://doi.org/10.1111/j.1346-8138.1987.tb03542.xTest
الإتاحة: https://doi.org/10.1111/j.1365-4362.1986.tb02216.xTest