Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Example Input: Abstract: Brain death is a condition widely recognized by philosophers, theologians, the public, and the law. Criteria for the determination of brain death have been progressively refined for almost 30 years. They involve clinical evidence of the loss of brain function and various periods of observation, which can often be shortened by confirmatory tests, particularly cerebral blood flow studies or electroencephalography. Prompt declaration of brain death is therefore possible. In addition, it is important for physicians to offer the possibility of organ donation to the patient's family both because organs are desperately needed and because many families desire this. A model algorithm for the determination of brain death, explanatory text, and appropriate references are presented to aid the development of protocols for individual and hospital use.
Example Output: Algorithms

Example Input: Abstract: CT of compression fractures is a useful adjunct to the plain x-ray in excluding signs of metastasis. However, increased bone density on CT may not distinguish osteoporotic fractures from neoplastic disease, in which case radioiodine scan, bone and marrow biopsies, or myelography may be necessary. Surgery for painful osteoarthritic spinal disease is controversial. The potential advantages of surgery must be weighted against the risk of anesthesia, the length and tolerance of postoperative immobility, and the effect of laminectomy and fusion on the biomechanics of the spine. Furthermore, the elderly are at increased risk for postoperative complications.
Example Output: Aged

Example Input: Abstract: A case is reported in which an epithelioid sarcoma developed in an apparently benign enchondroma or bone infarct at the site of a chrome-cobalt total knee replacement.
Example Output:
Aged