In the 1990s, when I decided to go beyond just collecting clippings and observations about single life, and look into the state of the published research, I consulted the definitive sourcebook for social psychological research.
The Handbook of Social Psychology is quite prestigious. Just about every graduate student in social psychology consults it, and most professors have it on their bookshelf. It is updated periodically. The first set of volumes was published in 1954, then updated in 1969, then again in 1985, and still again in 1998, which was the most recent version available to me at the time.
I looked in every index of every volume for some indication that social psychologists had something to say about single life. There was nothing.
Discovering that my cherished academic discipline was so silent about single life was one of the many motivators for my own research efforts.
I still have all of the volumes of all of the editions I consulted at the time, including even the very hard-to-find 1954 volumes. I even have extras of some of them. So I just made some of them available for sale at Amazon.com, using my own name as the seller. If you know of anyone who may be interested in these social psychological classics, feel free to spread the word.