Like G6PD which has only ever appeared in one (disastrous) viva, sickle cell disease has only ever made one appearance, in Question 12.1 from the first paper of 2014. If we are lucky, it will never come back. If we are slightly less lucky, the repeat question will again ask about the precipitants and the management. In brief, the precipitants can be broadly described as "stressors", and management depends somewhat on what sort of crisis it is. They come in vasoocclusive, aplastic and sequestration flavours. All will require oxygen, analgesia and rehydration, and most will require blood transfusion.
The exam candidate with an average lifespan would likely find it wasteful to dedicate an excess of reading time to this problem. Therefore, if one were to only read a single paper on this topic, it should be the 2004 article by Iheanyie Okpala. Or, one may safely restrict their reading to the LITFL sickle cell page.
The precipitants:
Most sicle cell crisis patients will require blood transfusion. As to what kind of blood transfusion, that depends on the severity. In general, it is reserved for people with a dropping haemoglobin, but realistically, that's all of them. "Transfusion is not recommended in uncomplicated painful crises but should be considered if there is a substantial drop in Hb from baseline (e.g. > 20 g/l or to Hb < 50 g/l), haemodynamic compromise or concern about impending critical organ complications" recommends Bernard et al (BJH Guidelines, 2016) with a Grade C level of conviction. If the addition of a little healthy haemoglobin is not effective, all the blood may need to be replaced with an exchange transfusion.
Okpala, Iheanyi E. "Sickle cell crisis." Practical Management of Haemoglobinopathies (2004): 63-71.
Walker, H. Kenneth, et al. "Peripheral blood smear." (1990). in Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.
Bessis, Marcel. "Codocytes and Target Cells." Corpuscles. Springer Berlin Heidelberg, 1974. 59-64.
Jones, Kathy W. "Evaluation of Cell Morphology and Introduction to Platelet and White Blood Cell Morphology." I do not know which textbook this is form, but it is a chapter which is available for free online ... for now.
Bull, BRIAN S., J. Breton-Gorius, and E. Beutler. "Morphology of the erythron."New York, McGraw Hill (2001): 271-288. - this is an online re-posting of a chapter of Williams' Haematology, but without the figures.
Davis, Bernard A., et al. "Guidelines on red cell transfusion in sickle cell disease. Part I: principles and laboratory aspects." British journal of haematology 176.2 (2017): 179-191.
Davis, Bernard A., et al. "Guidelines on red cell transfusion in sickle cell disease Part II: indications for transfusion." British journal of haematology 176.2 (2017): 192-209.