Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Code | Year | Code | Year | Code | Year |
| --- | --- | --- | --- | --- | --- |
| A | 1927 | A1 | 1955 | A2 | 1981 |
| B | 1928 | B1 | 1956 | B2 | 1982 |
| C | 1929 | C1 | 1957 | C2 | 1983 |
| CH | 1930 | CH1 | RIEN | CH2 | RIEN |
| D | 1931 | D1 | 1958 | D2 | 1984 |
| E | 1932 | E1 | 1959 | E2 | 1985 |
| F | 1933 | F1 | 1960 | F2 | 1986 |
| G | 1934 | G1 | 1961 | G2 | 1987 |
| H | 1935 | H1 | 1962 | H2 | 1988 |
| I | 1936 | I1 | 1963 | I2 | 1989 |
| J | 1937 | J1 | 1964 | J2 | 1990 |
| K | 1938 | K1 | 1965 | K2 | 1991 |
| L | 1939 | L1 | 1966 | L2 | 1992 |
| LL | 1940 | LL1 | RIEN | LL2 | RIEN |
| M | 1941 | M1 | 1967 | M2 | 1993 |
| N | 1942 | N1 | 1968 | N2 | 1994 |
| Ñ | 1943 | Ñ1 | 1969 | Ñ2 | 1995 |
| O | 1944 | O1 | 1970 | O2 | 1996 |
| P | 1945 | P1 | 1971 | P2 | 1997 |
| Q | 1946 | Q1 | 1972 | Q2 | 1998 |
| R | 1947 | R1 | 1973 | R2 | 1999 |
| S | 1948 | S1 | 1974 | S2 | 2000 |
| T | 1949 | T1 | 1975 | T2 | 2001 |
| U | 1950 | U1 | 1976 | U2 | 2002 |
| V | 1951 | V1 | 1977 | V2 | 2003 |
| X | 1952 | X1 | 1978 | X2 | 2004 |
| Y | 1953 | Y1 | 1979 | Y2 | 2005 |
| Z | 1954 | Z1 | 1980 | Z2 | 2006 |
Question:
list each code not associated to a year.
Answer:
CH1, CH2, LL1, LL2