public int TotalCitationsUntil(int year) => Papers .SelectMany(i => i.CitedIn) .Count(i => i.Years.Any(y => y <= year));
public int NumberOfCitationsInYear(int year) => Papers .SelectMany(i => i.CitedIn) .Count(i => i.Years.Contains(year));
public int TotalCitationsUntil(int year) => Papers .SelectMany(i => i.CitedIn) .Count(i => i.Years.Any(y => y <= year));
public int NumberOfCitationsInYear(int year) => Papers .SelectMany(i => i.CitedIn) .Count(i => i.Years.Contains(year));