What is the passive form of the following active sentence? "For my research, I have painstakingly collected antique maps from various libraries around the world over several years.
1
Over several years, various libraries around the world have been painstakingly contributing to my research by providing antique maps.
2
The antique maps from various libraries around the world have been painstakingly collected for my research over several years.
3
Over several years, my research has been supported by various libraries around the world that have provided antique maps.
4
The research of mine has been relying on the antique maps that have been collected from various libraries around the world over several years.
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