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:
| District | Incumbent | Party | First elected | Result | Candidates |
| --- | --- | --- | --- | --- | --- |
| Pennsylvania 4 | Herman Toll | Democratic | 1958.0 | Re-elected | Herman Toll (D) 64.1% James R. Cavanaugh (R) 35.9% |
| Pennsylvania 7 | William H. Milliken, Jr. | Republican | 1958.0 | Retired Republican hold | George Watkins (R) 51.1% Leonard Bachman (D) 48.9% |
| Pennsylvania 9 | Paul B. Dague | Republican | 1946.0 | Re-elected | Paul B. Dague (R) 57.7% John A. O'Brien (D) 42.3% |
| Pennsylvania 20 | Elmer J. Holland | Democratic | 1956.0 | Re-elected | Elmer J. Holland (D) 74.4% Ronald Bryan (R) 25.6% |
| Pennsylvania 23 | Albert W. Johnson | Republican | 1963.0 | Re-elected | Albert W. Johnson (R) 54.9% John Still (D) 45.1% |
| Pennsylvania 25 | Frank M. Clark | Democratic | 1954.0 | Re-elected | Frank M. Clark (D) 70.3% John Loth (R) 29.7% |
Question:
What district is incumbent elmer j. holland from?
Answer:
Pennsylvania 20