public partial class spp
    {       
        public spp()
        {
            this.spp_authors = new HashSet<spp_authors>();
        }
    
        public int id { get; set; }
        public Nullable<int> numspp { get; set; }
        public string textspp_1 { get; set; }        
        //еще куча свойств
        public virtual ICollection<spp_authors> spp_authors { get; set; }
    }

public partial class spp_authors
    {
        public int id { get; set; }
        public <int> idspp { get; set; }
        public <int> idauthor { get; set; }
    
        public virtual author author { get; set; }
        public virtual spp spp { get; set; }
    }