Perhaps you should try some spelling variations:
"elemental rf algorithm" » "elemental rd algorithm" (Expand Search), "elemental _ algorithms" (Expand Search), "elementary rf algorithm" (Expand Search), "elements rf algorithm" (Expand Search), "elementsal rf algorithm" (Expand Search)
"elemental pso algorithm" » "elementary pso algorithm" (Expand Search), "elements pso algorithm" (Expand Search), "elementsal pso algorithm" (Expand Search)
"element tracking algorithm" » "elements tracking algorithm" (Expand Search), "element training algorithm" (Expand Search), "element taking algorithm" (Expand Search)

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("elemental pso algorithm") OR ("elemental rf algorithm"))) OR ("element tracking algorithm"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"elemental pso algorithm\") OR (\"elemental rf algorithm\"))) OR (\"element tracking algorithm\"))".
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• Adding a wildcard symbol may retrieve word variants: (((("elemental pso algorithm") OR ("elemental rf algorithm"))) OR ("element tracking algorithm"))*.