▁and ▁included ▁in ▁Exp and ed ▁Un iverse , ▁Hein lein ▁writes : ▁The ▁L ens man ▁[ series ] ▁was ▁left ▁un fin ished . ▁There ▁was ▁to ▁have ▁been ▁at ▁least ▁a ▁sevent h ▁volume . ▁As ▁always , ▁Doc ▁had ▁worked ▁it ▁out ▁in ▁great ▁detail , ▁but ▁never ▁( so ▁far ▁as ▁I ▁know ) ▁wrote ▁it ▁down ▁... ▁because ▁it ▁was ▁un publish able — then . ▁But ▁he ▁told ▁me ▁the ▁ending ▁or ally ▁and ▁in ▁private . ▁ ▁I ▁sh an ' t ▁repeat ▁it ; ▁it ▁is ▁not ▁my ▁story . ▁Poss ibly ▁somewhere ▁there ▁is ▁a ▁manuscript — I ▁hope ▁so ! ▁All ▁I ▁will ▁say ▁is ▁that ▁the ▁ending ▁develop s ▁by ▁in es cap able ▁logic ▁from ▁cl ues ▁in ▁Children ▁of ▁the ▁L ens . ▁ ▁On ▁July ▁ 1 4 , ▁ 1 9 6 5 , ▁Smith ▁gave ▁written ▁permission ▁to ▁William ▁B . ▁Ell ern ▁to ▁continue ▁the ▁L ens man ▁series , ▁which ▁led ▁to ▁the ▁publishing ▁of ▁" M oon ▁Pro spect or " ▁in ▁ 1 9 6 6 , ▁New ▁L ens man ▁( which ▁contained ▁" M oon ▁Pro spect or ") ▁in ▁ 1 9 7 5 ▁and ▁Tri plan et ary ▁Agent ▁in ▁ 1 9 7 8 . ▁ ▁Three ▁additional ▁L ens men ▁nov els ▁that ▁feature ▁the ▁al ien ▁Second - Stage ▁L ens men ▁( known ▁as ▁the ▁Second - Stage ▁L ens man ▁Tr il ogy