Perhaps you should try some spelling variations:
"coder implementation _ planning problem" » "code implementation _ planning problem" (Expand search), "decoder implementation _ planning problem" (Expand search), "model implementation _ planning problem" (Expand search), "coder implementation _ packing problem" (Expand search), "coder implementation _ planning process" (Expand search)
"python codigo python python programming" » "python coding python python programming" (Expand search), "python code python python programming" (Expand search), "python codigo pythons python programming" (Expand search), "python codigo piton python programming" (Expand search), "python codigo pitons 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: "((\"coder implementation _ planning problem\") OR (\"python codigo python python programming\"))~".
• Removing quotes may allow a broader search: (( coder implementation _ planning problem ) OR ( python codigo python python programming ))~.
• Adding a wildcard symbol may retrieve word variants: (("coder implementation _ planning problem") OR ("python codigo python python programming"))*.