Perhaps you should try some spelling variations:
"advanced formulation using refractive errors" » "advanced modulation using refractive errors" (Expand search), "advanced simulation using refractive errors" (Expand search), "advanced calculation using refractive errors" (Expand search), "advanced formulations using refractive errors" (Expand search), "advanced formation using refractive errors" (Expand search), "advanced formulation using reactive errors" (Expand search), "advanced formulation using refractance errors" (Expand search), "advanced formulation using restrictive errors" (Expand search)
"using coding python python programming" » "using codigo python python programming" (Expand search), "using codigos python python programming" (Expand search), "using using python python programming" (Expand search), "using coding pythons python programming" (Expand search), "using coding piton python programming" (Expand search), "using coding pitons python programming" (Expand search), "using coping python python programming" (Expand search), "using coating python python programming" (Expand search), "using cooking python python programming" (Expand search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"advanced formulation using refractive errors\") OR (\"using coding python python programming\"))~".
• Removing quotes may allow a broader search: (( advanced formulation using refractive errors ) OR ( using coding python python programming ))~.
• Adding a wildcard symbol may retrieve word variants: (("advanced formulation using refractive errors") OR ("using coding python python programming"))*.