Perhaps you should try some spelling variations:
"element modeling algorithm" » "element scheduling algorithm" (Expand Search), "elements modeling algorithm" (Expand Search)
"level using algorithm" » "level cosine algorithm" (Expand Search), "level fusion algorithm" (Expand Search)
"element tree algorithms" » "elements tree algorithms" (Expand Search), "element three algorithms" (Expand Search), "element free algorithms" (Expand Search)

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("element modeling algorithm") OR ("element tree algorithms"))) OR ("level using algorithm"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"element modeling algorithm\") OR (\"element tree algorithms\"))) OR (\"level using algorithm\"))".
• Removing quotes may allow a broader search: (((( element modeling algorithm ) OR ( element tree algorithms ))) OR ( level using algorithm )).
• Adding a wildcard symbol may retrieve word variants: (((("element modeling algorithm") OR ("element tree algorithms"))) OR ("level using algorithm"))*.