Novi Commentarii academiae scientiarum Petropolitanae 20, 1776, pp. 189–207 (E478) PDF
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Robert J. Twiss; Eldridge M. Moores «§2.1 The orientation of structures». A: Structural Geology. 2a edició. Macmillan, 1992, p. 11. ISBN 0-7167-2252-6. «...the attitude of a plane or a line — that is, its orientation in space — is fundamental to the description of structures.»