\begin{thebibliography}{999}

\bibitem{MG} M.B.Green, Scientific American {\bf 255} (Sept.1986) 48.
\bibitem{LSW}	W. Lerche, A. N. Schellekens and N. Warner, \\
	\PR{177} (1989) 1. 
\bibitem{GSW} M.B.Green, J.H.Schwarz and E.Witten, {\em Superstring Theory},
          \\   Cambridge Univ. Press, (1987).
\bibitem{LS}   W. Lerche and A.N. Schellekens, {\em The covariant lattice
	construction of four-dimensional strings}, lectures at the Summer 
	School on Strings and Superstrings, Romania, September 1987. CERN
	preprint TH.4925/88 (1988).
\bibitem{BN} B.E.W.Nilsson, {\em A Course in String Theory},\\ G\"{o}teborg
 1987-1988, (unpublished notes).
\bibitem{G} P.Ginsparg, {\em Applied Conformal Field Theory},\\ Les Houches,
Session XLIX (1988), HUPT-88/A054.
\bibitem{P} M.Peskin, {\em Introduction to String and Superstring Theory II},
 \\ Santa Cruz Lectures, June 1986, SLAC-PUB-4251.
\bibitem{Sh} J.Scherk, Rev.Mod.Phys.{\bf 47} (1975) 123.
\bibitem{Yang}	S.-K. Yang, 	\NP{B285[FS19]} (1987) 183; \\ 
           S.-K. Yang and H.B.Zheng, 	\NP{B285[FS19]} (1987) 410. 
\bibitem{DVV1} R.Dijkgraaf, E.Verlinde and H.Verlinde, {\em Conformal Field
  Theory at c=1}, 1987 Carg\'{e}se Summer School on Nonperturbative Quantum Field
  Theory; \\
              P.Ginsparg, \NP{B295[FS21]} (1988) 153. 
\bibitem{VirS} M.A.Virasoro, Phys.Rev.{\bf 177} (1969) 2309; \\
               J.A.Shapiro, \PL{338} (1970) 361.
\bibitem{Crem} E.Cremmer and J.Scherk, \NP{B103} (1976) 399.
\bibitem{Sw} J.H.Schwarz, \PR{89} (1982) 223.
\bibitem{BPZ} A.Belavin, A.Polyakov and A.Zamolodchikov, \\ \NP{B241} (1984)
333. 
\bibitem{Vir} M.A.Virasoro, Phys.Rev.{\bf D1} (1970) 2933.
\bibitem{BOS}	L.Brink, D.Olive and J.Scherk, \NP{B61} (1973) 173.
\bibitem{Gli} F.Gliozzi, Nuovo Cim.Lett. {\bf 2} (1969) 846.
\bibitem{Verma} D.-N.Verma, Bull.Amer.Math.Soc. {\bf 74} (1968) 160.
\bibitem{Shap} J.A.Shapiro, Phys.Rev.{\bf D5} (1972) 1945.
\bibitem{GQ}	D. Gepner and Z.Qiu, \NP{B285[FS19]} (1987) 423.
\bibitem{KM} V.Kac, Math.USSR Izv. {\bf 2} (1968) 1271; \\
             J.Moody, J.Algebra, {\bf 10} (1968) 211.
\bibitem{Lep} J.Lepowsky and R.L.Wilson, \CMP{62} (1978) 43.
\bibitem{GW}	D. Gepner and E. Witten, \NP{B278} (1986) 493.
\bibitem{C} J.Cardy, \NP{B270[FS16]} (1986) 187.
\bibitem{CIZ1}    A. Cappelli, C.Itzykson and J.-B. Zuber, \NP{B280} (1987)
445.  
\bibitem{CIZ2}    A. Cappelli, C.Itzykson and J.-B. Zuber,
	 \\  \CMP{113} (1987) 1; \\
  	A. Kato, \MPL{A2} (1987) 585.
\bibitem{N}	K.S.Narain, \PL{B169} (1986) 41.
\bibitem{NSW}	K.S.Narain, M.H.Sarmadi and  E.Witten, 	\NP{B279} (1987) 369. 
\bibitem{GO1}P. Goddard and D. Olive, in {\em Vertex
 Operators in Mathematics and Physics}, Springer Verlag (1984). 
\bibitem{GO2}P. Goddard and D. Olive, \JMP{A1} (1986) 303.
\bibitem{CN}M.Caselle and	K.S.Narain, 	\NP{B323} (1989) 673. 
\bibitem{V} E.Verlinde, 	\NP{B300} (1988) 360; \\
  G.Moore and N.Seiberg, \PL{B212} (1988) 451. 
\bibitem{TG} T.Gannon, {\em Lattices and Theta Functions}, PhD Thesis (1991),
  \\ McGill Univ., Montreal (unpublished).
\bibitem{CS} J.H.Conway and N.J.A.Sloane, {\em Sphere Packings, Lattices and
  Groups}, (Springer Verlag, New York, 1988).
\bibitem{GL1} T.Gannon and C.S.Lam, Phys.Rev.{\bf D41} (1990) 492.
\bibitem{Nie} H.Niemeier, Journal of Number Theory {\bf 5} (1973) 142.
\bibitem{Lee} J.Leech, Canadian Journal of Mathematics {\bf 19} (1967) 251.
\bibitem{GL2} T.Gannon and C.S.Lam, Rev.Math.Phys.{\bf 3} (1991) 331.
\bibitem{GSW385} J.Scherk and J.H.Schwarz, \NP{B81} (1974) 118.
\bibitem{CHSW}    P. Candelas, G. Horowitz, A. Strominger and E. Witten,
 \\ \NP{B258} (1985) 46. 
\bibitem{GKMR}	B. Greene, K.H. Kirklin, P.J. Miron and G.G. Ross,
	\PL{B180} (1986) 69; \NP{B278} (1986) 667; \NP{B279} (1986) 574.
\bibitem{DHVW}	L. Dixon, J. Harvey, C. Vafa and E. Witten, \\
	\NP{B261} (1985) 678; \NP{B274} (1986) 285.
\bibitem{IMNQ}	 L.E. Ib\'{a}\~{n}ez, J. Mas, H.-P. Nilles and F. Quevedo,
	  \\  \NP{B301} (1988) 157.
\bibitem{KLT}  H. Kawai, D.C. Lewellen and S.-H.H. Tye,
	\PRL{57} (1986) 1832; \NP{B288} (1987) 1.
\bibitem{AEHN}	I. Antoniadis, J. Ellis, J.S. Hagelin and D.V. Nanopoulos,
	\PL{B205} (1988) 457.
\bibitem{LLS}	W. Lerche, D. L\"{u}st and A.N. Schellekens,
	\PL{B181} (1986) 71; \NP{B287} (1987) 477.
\bibitem{LNS}	W. Lerche, B.E.W. Nilsson and A.N. Schellekens,
  \\	\NP{B294} (1987) 136; \\	
       W. Lerche, B.E.W. Nilsson, A.N. Schellekens and N.A.Warner,
	\NP{B299} (1988) 91. 
\bibitem{SW}	A.N. Schellekens and N.A.Warner, \NP{B308} (1988) 397;
\NP{B313} (1988) 41.
\bibitem{LSW2}  W. Lerche, A.N. Schellekens and N.P. Warner, \\ CERN preprint
	TH.5155/88 (1988).
\bibitem{GSW384} J.Scherk, \NP{B31} (1971) 222; \\
               A.Neveu and J.Scherk, \NP{B36} (1972) 155.
\bibitem{PG} D.Gross and V.Periwal, Princeton preprint-1090(1988).
\bibitem{Nam} Y.Nambu, in {\em Symmetries and quark models}, ed. R.Chand,
(Gordon and Breach, 1970) 296; \\
   H.B.Nielsen, {\em An almost physical interpretation of the integrand of
the n-point Veneziano model}, The 15th International Conf. on High energy
Physics, Kiev (1970); \\
   L.Susskind, Nuovo Cim. {\bf 69A} (1970) 457.
\bibitem{EngN} F.Englert and A.Neveu, \PL{B163} (1985) 349.
\bibitem{FMS} D.Friedan, E.Martinec and S.Shenker, \NP{B271} (1986) 93. 
\bibitem{Poly} A.Polyakov, \PL{B103} (1981) 207; \\
               A.Polyakov, \PL{B103} (1981) 211.
\bibitem{Pol} J.Polchinsky,  \CMP{104} (1981) 207.
\bibitem{GSW142} L.D.Faddeev and V.N.Popov, \PL{B25} (1967) 29.
\bibitem{BRST} C.Becchi, A.Rouet and R.Stora, \PL{B52} (1974) 344; \\
                C.Becchi, A.Rouet and R.Stora, Ann.Phys. {\bf 98} (1976)
287;\\ 
            I.V.Tyupin, Lebedev preprint FIAN No. 39 (1975).
\bibitem{GSW280} M.Kato and K.Ogawa, \NP{B212} (1983) 443; \\
               S.Hwang, Phys.Rev.{\bf D6} (1983) 2614.
\bibitem{FV} S.Fubini and G.Veneziano, Nuovo Cim. {\bf 67A} (1970) 29.
\bibitem{GSW56} L.Brink, P.DiVecchia and P.Howe, \PL{B65} (1976) 471; \\
                S.Deser and B.Zumino, \PL{B65} (1976) 396.
\bibitem{NS} A.Neveu and J.H.Schwarz, \NP{B31} (1971) 86.
\bibitem{Spin} C.Thorn, Phys.Rev.{\bf D4} (1971) 1112; \\
               J.H.Schwarz, \PL{B37} (1971) 315; \\
               E.Corrigan and D.Olive, Nuovo Cim. {\bf 11A} (1971) 749; \\
               E.Corrigan and P.Goddard, Nuovo Cim. {\bf 18A} (1973) 339.
\bibitem{Ram} P.Ramond, Phys.Rev.{\bf D3} (1971) 2415.
\bibitem{KLL} V.A.Kostelecky, O.Lechtenfeld, W.Lerche, S.Samuel,
              S.Watamura \NP{B288} (1987) 173.
\bibitem{HBFK} M.Halpern, Phys.Rev.{\bf D12} (1975) 1684;  \\
          T.Banks, D.Horn and H.Neuberger, \NP{B108} (1976) 119;  \\
          I.Frenkel and V.Kac, Invent.Math. {\bf 62} (1980) 23;  \\
          G.Segal, \CMP{80} (1981) 301.
\bibitem{FMS60} E.Martinec, Phys.Rev.{\bf D28} (1983) 2604.
\bibitem{FF}	B.L.Feigin and D.B.Fuchs,
	        \FA{16,N2} (1982) 47; \FA{13,N4} (1989) 91; \\
	         Vl.S.Dotsenko and V.A.Fateev,
	         \NP{B248[FS12]} (1984) 312; \NP{B251[FS13]} (1985) 691; \\
          G.Felder, \NP{B317} (1989) 215. 
\bibitem{GSW193} J.L.Gervais and B.Sakita, \NP{B34} (1971) 632.
\bibitem{GSB} M.B.Green and J.H.Schwarz, \NP{B181} (1981) 502; \\
              L.Brink, M.B.Green and J.H.Schwarz, \NP{B198} (1982) 474.
\bibitem{CFQS} J.Cohn, D.Friedan, Z.Qui, S.Shenker, \NP{B278} (1986) 577.
\bibitem{LTZ} L\"{u}st, S.Theisen and G.Zoupanos, \NP{B296} (1988) 800.
\bibitem{LL}	W.Lerche and D. L\"{u}st, \PL{B187} (1987)
457;  \\
         	W. Lerche, D. L\"{u}st and A.N. Schellekens, \PL{B181} (1986) 71.
\bibitem{GHMR} D.Gross, J.Harvey, E.Martinec and R.Rohm, \NP{B260} (1985) 589; 
           \NP{B267} (1986) 75.
\bibitem{ENS} F.Englert, H.Nicolai and A.N.Schellekens, \NP{B274} (1986) 315.
\bibitem{S} A.N.Schellekens, \PL{B184} (1987) 427.
\bibitem{LT} L\"{u}st and S.Theisen, \NP{B302} (1988) 499.
\bibitem{Gep} D.Gepner, \NP{B296} (1988) 757.
\bibitem{FIQS} A.Font, L.E.Ib\'{a}\~{n}ez, F.Quevedo and A.Sierra, \\ \NP{B337}
(1989) 119.
\bibitem{GKO} P.Goddard, A.Kent and D.Olive, \CMP{103} (1986) 105.
\bibitem{KS} Y.Kazama and H.Suzuki, \NP{B321} (1989) 232.
\bibitem{SY} A.N.Schellekens and S.Yankielowicz, \NP{B327} (1989) 673;
	             \PL{B227} (1989) 387.
\bibitem{Wit} E.Witten, Phys.Rev.{\bf D44} (1991) 314;  \\
        R.Dijkgraaf, E.Verlinde and H.Verlinde, Princeton preprint 
         PUPT-1252 (1991); \\
        A.Giveon, Mod.Phys.Lett. A6 (1991) 125.
\bibitem{BNem} I.Bars and D.Nemeschansky, \NP{B348} (1991) 89.
\bibitem{DLP} L.Dixon, J.Lykken and M.Peskin, \NP{B325} (1989) 329; \\
              P.Griffin and O.Hernandez, \NP{B356} (1991) 287.
\bibitem{Bal} J.Balog, L.O'Raifeartaigh, P.Forgacs and A.Wipf, \NP{B325}
                (1989) 225; \\
\bibitem{Pet} P.Petropoulos, \PL{B236} (1990) 151; \\
            N.Mohammedi, \JMP{A5} (1990) 3201.
\bibitem{Hw} S.Hwang, \NP{B354} (1991) 100.
\bibitem{HwR} S.Hwang and P.Roberts, (work in progress).
\bibitem{Wit2}  E.Witten, \CMP{92} (1984) 455.
\bibitem{SW2}	A.N. Schellekens and N.A.Warner, \PL{B177} (1986) 317;
\PL{B181} (1986) 339; \NP{B287} (1987) 317.
\bibitem{Zam} A.Zamolodchikov, Theor.Math.Phys, {\bf 65} (1986) 1205.
\bibitem{O} D.Olive, {\em Kac-Moody Algebras: an introduction for physicists}
           Imperial College preprint TP/84-85/14.
\bibitem{Kac} V.G. Ka\v{c}, {\em Infinite Dimensional Lie Algebras},
            (Birkhauser, Boston, 1983).
\bibitem{KP} V.G. Ka\v{c} and D.H. Peterson, Advances in Math. {\bf 53}
            (1984) 125.
\bibitem{CR}	P. Christe and F. Ravanini,
	\JMP{A4} (1989) 897.
\bibitem{BI}  M.Bauer and C.Itzykson, \CMP{127} (1990) 617; \\
              Ph.Ruelle, E.Thiran and J.Weyers, \CMP{133} (1990) 305; \\
              Ph.Ruelle, \CMP{133} (1990) 181; \\
\bibitem{War} N.P.Warner, \CMP{130} (1990) 205; \\
\bibitem{KW} V.G. Ka\v{c} and M.Wakimoto, Proc.Natl.Acad.Sci, USA {\bf 85}
            (1988) 4956; \\
            S.Lu,\PL{B218} (1989) 46. \\
            I.C.Koh and P.Sorba, \PL{B215} (1988) 723.
\bibitem{Sug} H.Sugawara, Phys.Rev.{\bf 170} (1968) 1659.
\bibitem{Weyl} H.Weyl, {\em Gesammelte Adhandlungen}, \\
   (Springer-Verlag, Heidelberg, 1968).
\bibitem{WK} V.G.Ka\v{c}, J.Funct.Anal.Appl. {\bf 80} (1974) 68.
\bibitem{GR} T.Gannon and P.Roberts (work in progress).
\bibitem{GanP} T.Gannon (private communication).
\bibitem{TGan} T.Gannon, {\em Heterotic Partition Functions}, (in preparation).
\bibitem{Wyb} B.G.Wybourne, {\em Classical Groups for Physicists}, (Wiley,
1974). 
\bibitem{GT} P.Goddard and C.Thorn, \PL{B40} (1972) 235; \\
             R.Brower, Phys.Rev.{\bf D6} (1972) 1655.
\bibitem{GN} J.-L.Gervais and A.Neveu, \NP{B238} (1984) 396; \\
              \PL{B151} (1985) 271;
\bibitem{Ger} J.-L.Gervais, LPTENS-90/13 preprint (1990); \\
              \PL{B243} (1990) 85; \CMP{130} (1990) 257.
\bibitem{Kai} R.K.Kaiser, ETH-Z\"{u}rich preprint, ETH-TH/90-40 (1990).
\bibitem{CY3} S.T.Yau, in {\em Symposium on Anomalies, Geometry and
Topology}, ed. W.A.Bardeen and A.R.White (World Scientific, Singapore,
1985);\\
P.Candelas, A.Dale, C.L\"{u}tken and R.Schimmergk, \NP{B298} (1988) 493; \\
P.Candelas, C.L\"{u}tken and R.Schimmergk, \NP{B306} (1988) 113; \\
P.Aspimwall, B.Greene, K.Kirklin and P.Miron, \NP{B294} (1987) 193.
\bibitem{Font} A.Font, L.E.Ib\'{a}\~{n}ez and F.Quevedo, \PL{B217} (1989) 271.


\end{thebibliography}
