8Channing A, Butler B I. Cryogenic opal: a deposition from Yellowstone hot springs[J]. Earth and Planetary Science Letters, 2007, 257:121 - 131.
9Miaserref Onal, Sibel Kahraman, Ytiksel Sarikaya. Differentiation of a-cristobalite from opals in bentonites from Turkey [J]. Applied Clay Science, 2007, 35:25 - 30.
10Muserref Onal, Yh ksel Sarikaya. The effect of heat treatment on the paracrystallinity of an opal - CT found in a bentonite[J]. Journal of Non-Crystalline Solids, 2007, 353:4195-4198.