#include <bits/stdc++.h>
using namespace std;
int dx[4] = {0, 1, 0, -1};
int dy[4] = {-1, 0, 1, 0};
int H, W;
vector<string> data;
bool check_around(int x, int y) {
  for (int i = 0; i < 4; i++) {
    int nx = x + dx[i];
    int ny = y + dy[i];
    if (nx < 0 || nx >= W || ny < 0 || ny >= H) continue;
    if (data[ny][nx] == '#') return true;
  }
  return false;
}
int main() {
  cin >> H >> W;
  data.resize(H);
  for (int i = 0; i < H; i++) {
    cin >> data[i];
  }
  string ans = "Yes";
  bool OK = true;
  int cnt = 0;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (data[i][j] == '#') {
        cnt++;
        OK = check_around(i, j);
        if (!OK) {
          ans = "No";
          break;
        }
      }
    }
    if (!OK) break;
  }
  if (cnt < 2) ans = "No";
  cout << ans << endl;
  return 0;
}
