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Well it sounds like you've been careful on the approach to building the links. Have you analysed the websites above you (with a fine tooth comb) and critically analysed yours as if it was someone else's? I know it's frustrating, but I'd say remain patient and just remain ethical. It may be the case that these .gov links look good because of their 'authority' but the actual relevance of them to your site may not be ticking boxes. You'd be better getting a natural link from a .co.uk or .net, for example, rather than trying to sap authority. What's more, if the .gov sites are already linking out to others - remember that you're sharing the link benefit with all those other sites, so it may not actually be that valuable. Try and explore other ways you can get links in your niche rather than asking for them - the rankings will come naturally then!