Cancer Prevention Fellowship Program, Office of Preventive Oncology, National Cancer Institute, Bethesda, MD 20892-7105, USA. This article has been cited by other articles in PMC. Abstract. Causation is an essential concept in epidemiology, yet there is no single, clearly articulated definition for the discipline. From a systematic review of the literature, five categories can be delineated: production, necessary and sufficient, sufficient-component, counterfactual, and probabilistic.
Broad Valley. Broad Valley (63Â°22â²S 57Â°55â²W / 63.367Â°S 57.917Â°W / -63.367; -57.917Coordinates: 63Â°22â²S 57Â°55â²W / 63.367Â°S 57.917Â°W / -63.367; -57.917) is a descriptive name for the broad glacier-filled valley on the south side of Laclavere Plateau, Trinity Peninsula. The name was suggested by V.I.
Roof valleys are troughs that discard runoff water where two sections of sloped roof meet. The valleys on many older houses comprise layers of roofing paper, which can deteriorate over time. In other cases, shingles are overlapped to make a valley, and water from harsh rains can find a way under the shingles.